Go for a hosting that provides HTTP/2 support, PHP 7 and object caching. Then set your Wordpress with a caching plugin that uses the object caching, use a minify plugin too and make sure your images are compressed and resized accordingly.
Use as fewer plugins as possible and make sure your theme...
You can grow those domains too, but it will take a while and you'll have to put a lot of work in it. It's better to go for domains with higher metrics although they may not be as cheap since they will spare you the hassle.
Yup and on the long run it all breaks down to trial & error because there's no other way. If you wanna innovate and hit the jackpot you gotta fail a couple of times so you can learn and understand what you did wrong.
If places like fiverr or seoclerks wouldn't be full of shady gigs promising to put sites on 1st. page through actual spam then folks wouldn't be tricked into believing that getting results is as easy as making links, no matter what.
Developing based upon existing ideas isn't wrong, however it depends what you make different compared to the masses. That's what makes you grow further.
I can't fully agree with the claim that what everyone does is bad because at some extent it isn't. You're supposed to learn from your own...
Regenerate Thumbnails uses a great deal of resources, if you use that on shared hosting it might just kill your account temporary as the hosting will throttle you. I'd use that with care since although it's effective it is also inconvenient on some low resource hosting plans.