

uBlock Origin explicitly advises against this. If it’s the only content blocker it doesn’t currently have issues with YouTube, if you have multiple you’ll probably hit the “disable your adblocker” warning.
The first three are using identical techniques so combining them is of very limited benefit. They’re mostly there to cover software that doesn’t have an ad blocker.
I’d stick with just ublock origin.
No, the network effect is too strong. Deleting WhatsApp is cutting off the primary/only way to contact many friends (in countries where it’s the primary messenger), and a mild form of “abandon everything and go live in a monastery”.