No. You're just posting like you know everything about the matchup, called yourself the God of spacing (I chuckled, I'll admit), and you keep talking about these situations that 80% of the time won't happen how you want against an opponent who actually knows how to play well.
I play Jiggs. Very well. I have faced a plethora of Mewtwos on FG that actually knew what they were doing. I shit all over their day. The reverse is true as well, despite my most valiant efforts. Mewtwo can kill Jiggs with power, but Jiggs has far more options than he does.
By a god of spacing I meant things were extremely tight and I was lucky. It was meant in a somewhat sarcastic manner, which wasn't really what was conveyed clearly. I'm inclined to think uair can beat out dair, but I'm not sure [have heard the tail has no hurtbox, which if true, would mean uair just beats dair].
This Puff player is fairly solid, they've made the power rankings using only Puff in Melee, PM, and Smash 4, and are generally solid at spacing people out.
And it's called offering advice - being a good player is trying to make those situations come up in order to capitalize, which usually means forcing the opponent to make a mistake.
Well I ain't one for debate or discussion. Well actually I quite like discussion. But debate not so much.
To make this easier for me I take on each point that you make in order.
Why are you bringing up fox from melee? We are talking about Smash 4 in a Smash 4 discussion thread. Melee isn't applicable to Smash 4 in the slightest. All Smash games are all their own different entities and using another as a reference doesn't work to well to prove a point if that was what you were intending.
You never clarified if this puff player was actually good or not. Stating that you are fighting a local puff fighter leads me to believe he could simply be some casual player that plays smash. Especially if he apparently got hit with the spike. A good puff player knows how to dodge meteors and spikes. I have never seen Jiggs get spiked unless it was DK's fair. An easy air dodge and you're safe from all gimp moves. I'm going to assume this Puff player didn't know anything about how to play fight as puff.
Why was the puff using dair? Puff players go for fairs and bairs. You only mention stopping dair. Do you have no plans for stopping her best moves? Because believe it or not dair ain't that good. Also why would you dair teleport after a confusion. Unless you ledge cancel it you are completely vulnerable and you just put her in the air which is where she wants to be in the first place. "Gee thanks thor" Uair is slow by the time you do that move a good puff would of easily used one of her million jumps and jumped out the way and fast fall. or better yet just air dodged the move entirely. You're better off using nair if anything and I wouldn't even recommend that.
Dtilt will of course hit her if she crouch and yes, you can link it to utilt at like 0%. Real useful. Already told you jab does not hit crouch. In fact the main combos will not even work if you hit jab at all. since she is so light she flies just out of reach for any good set ups and will most likely hit you. You bring up bair again and I'll repeat to you. Bair is slow. You will not outspace jigglypuff with that bair. If shulk with his fast as hell fair and nair can get dodged by jigglypuff players than Mewtwo's bair is a breath of fresh air. Also good luck hitting a jigglypuff in the air with confusion. You either have to wait for just the right moment which may never come or just get lucky. Disable has a set knockback in air. It ain't near far enough to get someone off you. I can tell you what it is enough for. To make your opponent laugh at that lame attempt to stop them from going on the offensive.
Here's a good point. Shadow Ball IS a punish option. But do realize that pound will clank with projectiles if used right. This includes shadow ball. From what I gathered. Shadow ball is better used for mix ups as it can completely change Mewtwo's momentum and make some sick combos.
Good jigglypuffs know when to use rest. They will know when Mewtwo will die to it. And trust me he'll die early because he's super light. But yes if they somehow miss their rest punish with dsmash or better yet do a kill confirm uthrow.
This antiair thing isn't a thing sorry. usmash doesn't work that way. I played too many matches with and against mewtwo and I can honestly say it doesn't work as good as you say it does. If you hit someone with confusion they can do anything out of it. Jiggs can just jump and be out of range or better yet attack you. Plus if you miss your anitair usmash you will suffer for it.
I honestly think I learned mostly I there is to Mewtwo at the moment. And if you play online you'll see exactly how all Mewtwo players play. Because it's probably the same way I play. Furthermore, I never truly had problems with sheik players. Because, it was obvious what they wanted to do. And I read them like a book. Shieks tend to all want the same thing at the end of the day. But yes the match up is winnable but unlikely and not fun for mewtwo. I rather play palutena than play that shitty match up man. To let you know I played multiple sets against this guy regularly. I know this match up well and I know Mewtwo.
Stopping dair is important to recovery. That's something I picked up fairly quickly [Puff can insert herself right between you and the ledge and dair and you'll be hit out of teleport, and she can keep doing this over and over with all her jumps]. It's also important to make sure she can't try to contest you as she lands. If none of the Puffs you've been doing do this, they aren't contesting your recovery properly, which leads me to wonder what else they do differently.
Be facing away from Jigglypuff when in neutral - that leaves retreating bair and confusion [to reset the situation]. You can try to also punish with retreating nairs or fair, but bair has more range in exchange for being slower [fair is frame 7, bair is frame 12, nair is frame 6].
You don't hit them with confusion, disable, or shadow ball, you b-reverse the move to turn around and set up the chance to double jump bair or reverse uair. Perhaps I should've been clearer but I thought this point was fairly obvious since I said "you do those things to turn around".
If they're clanking shadow ball with pound you're not using it when I suggested - I said if they pound, react with shadow ball. Pound seems rather mediocre [outside of shield damage and the angle being somewhat useful for gimping], but if they're using pound to beat back shadow balls then they're just doing something right.
Dsmash kills WAY earlier than uthrow. Killing them with uthrow is good if you think you'll somehow mess up dsmash spacing, but fsmash is the optimal damage dealing punish and dsmash is the optimal KO punish.
Usmash is a risky anti-air, but if you read them it can work. It's not easy, but Smash is hard. It's also best used as an anti-air when they are low on jumps or have commited to a fast-falled aerial [which should be rare, but it happens]. I'm pretty sure utilt is a more reliable anti-air, but usmash is far more rewarding.
To claim you know the MU well after less than a week is very arrogant [unless you are also being sarcastic like I was when I said the word god (which is also a joke because of my name - not sure how you all missed that...)]. People claimed Snake bodied everyone in the first weeks of Brawl because of his huge damage tilts, grenades, and "crazy-good" recovery, and there were legitimate and large-scale tournaments where top placings were all Snake, including one where the top 5 players all solo-mained Snake. Nowadays, we know Snake loses to MK, Olimar, and DDD, and many outright refuse to fight ESAM's Pikachu, having backups for it. Olimar also moved from mid-tier to near the top.
I referenced Melee because I would rather play just about any Smash MU as Mewtwo [other than maybe Pikachu or one of the other best rushdown characters like Sheik and Fox? Even then, maybe not...] than I would fight Fox as Link in Melee. It may be the hardest MU you've ever played, but if a Brawl MK main was complaining about ICs and calling it the hardest MU he'd ever played, he wouldn't have much room to complain about hard MUs. You definitely have more with Puff Mewtwo but it seems that you think this is an impossible wall to climb after less than a week. Fighting hard MUs does mean you have to be a better player, but it's not impossible.
Also the matchup is easier on battlefield due to platforms. FD seems to make this MU worse because Mewtwo's confusion doesn't work as well and he doesn't have platforms to help him maneuver or get even earlier KOs on [say somehow getting a grab on the top platform into a uthrow].