If you're looking for Ryu guides then you can check out Hooded's youtube channel (
https://www.youtube.com/channel/UCBCmJgxi59OVOtT43mcOy4Q) He's got a ton of neat videos that show you some of the crazy things Ryu can do, and easy setups for them. I find he explains things in a way that's super easy to understand as well as being someone who's really on top of the meta as it's evolving.
In answer to your questions:
1. Yes he is definitely viable, and no you don't need to be crazy good to beat a Shiek. I play smash 4 casually compared to how much I play PM and Melee, yet I can go even with my old roommate who was the best Shiek in the region and has been maining her since smash 4 released. Shiek is, imo, a bad example as Ryu has the utilt infinite on her and every other fast faller. Yea it's difficult to get it started but you hit with one utilt and theoretically there goes that Shiek's stock. If you were to say do you need to be crazy good to beat a Sonic or Luigi or Rosaluma then yea you would need to be on par with the other players skill level. The top player in my region mains Pikachu which is arguably a poor matchup for Ryu from what I've read, but I can hold my own against him and while I might not always win, playing me in bracket is never free for him, even if he's the best player in my region. I find that if you can learn to implement some of Ryu's space controlling methods as well as some of his easier shield breakers (Shakunetsu hover into collarbone breaker, and DD2 into Shoryuken), then he becomes an incredibly potent character with relatively little techskill put in.
2. In melee I play Shiek, but in PM I play Wolf, so I know all about techskill and the different levels required for different characters. Ryu, imo, is no more difficult to learn than a spacie, with the added bonus of not having to learn a ton of shine shenanigans. Note I said learn, not play as. Ryu is magnitudes easier to play as properly than a spacie simply because he's in smash 4. I just mean that you can learn to do the true inputs, or DD, or Shaku Hover in about the same time it would take to learn to shine grab, waveshine, pillar with Falco, or shine into flash with Wolf. Sure the true inputs can be a little janky at times to perform, but I got those down consistently in about 20 minutes. A gamecube controller will do you just fine playing him and I can do any and all tech that has been discovered so far with the default button layout, I just play claw. I play Ryu in smash 4 mainly because he is so different from every one else. I play three games, Melee, PM, and Smash 4, and I've found that personally if I play the same character across different games I end up trying to do tech that I cant do in that game but could in another. It messes me up something fierce especially when my region's monthly plays all games in one day. So playing Ryu is nice
because he is so different. I don't find myself wanting to do a waveshine with him, or wanting to do chaingrabs, I find myself wanting to do Ryu things.
Really it just comes down to if you enjoy playing as Ryu, do you like controlling space, playing footsies, and, most of all, absolutely demolishing peoples shields? Then he's the character for you. You should never let the techskill required to play a character be what stops you from playing them, if anything it should be what drives you to play them. Practicing techskill and getting better execution will make your play across all games with all characters better.
Best of luck :3
