This is the one I’ve heard used most. It’s got everything from full sets to individual parts. https://www.bricklink.com/v2/main.page
If you aren’t sure what piece you are looking for but know what set its from you can look it up on this site http://www.peeron.com/ and then search bricklink by the piece item ID. Hope this helps
I usually watch YouTube on a laptop hooked up to my tv, so I downloaded freetube and just imported my subscriptions. It’s got sponsorblock and other features built in, but you can’t like or comment on videos. Overall though I’ve been using it for about 6 months now and wouldn’t dream of going back to YouTube and trying to constantly deal with them fucking it up more daily.