You can Shine->UpSmash from a Dthrow. Just need those quick fingers

Ok, Thanks! Do I have to Jump Cancel it? I usually try to read a roll/getup attack and punish with the USmash afterwards.

The Up-smash is only guaranteed if the other person doesn´t tech the throw and the shine is only used for a reset, and shine to Up-smash is possible just like in melee
I don´t know how to do it thought I´ve only seen it once done by Envy, he is a very technical online player.

If they don't tech, you Shine. If they're behind you when you Shine them, you'll have to turnaround, jump, and then usmash. I recommend having a dedicated C-stick up button (I use 2 and WASD for movement) just for things like this. The input sequence is grab -> down and hold the button -> shine and release both buttons -> turnaround if need be -> JC quickly! -> C-stick

Thanks man! Now I have actually some use for DThrow besides Jab Reset (which I dont like by the way)^^

And if I already ask, how do I have to time the input for the Illusion Cancel?

This might be DI-able as people have pointed out and tech-able (obviously) but if they mess up on both you can do:
Shine>Grab>Dthrow>TurnAround Shine>Grab>Dthrow>Rinse and Repeat, as a pseudo chain-grab.

Is Fox good now since the cast is more balanced?

Just wondering

Fox has been good for a while. I don't think he's better, because I think the Marth buff hurt him and a couple of other characters still give him a hard time, but I don't think he's bad.

presumably yes. would there be any reason at to why not?

What characters does fox have a bad match up against

Everyone with a sword, IMO.

Anyone who has quick disjoints, anyone who can juggle or chaingrab Fox too much, and characters who are really good at edgeguarding him offstage IMO.

Those can easily be argued for indeed. Consider that in Melee, Fox is even against Marth. This Marth is fairly close to Melee Marth and this Fox is nowhere near Melee Fox. At the very least, Fox's punish game on Mart isn't as strong as it was in the past (upthrow->uair doesn't work) and Marth still gets zero-to-deaths.

I also think very defensive/campy characters can eat Fox, like Zelda and Wario.

Those characters can't camp against Fox though. He can runaway laser-camp, then him them with an aerial, and runaway laser-camp against. You did that to me yesterday and I almost indefinitely lost to it. Blocking the lasers isn't hard, but Zelda's too slow to catch Fox, and he can easily punish any teleport mix-up attempt.