That's an impossible question to answer, difference FOSS apps are different, but installing one shouldn't break another.

Absolutely not. Always use front-ends. If you're going to Reddit, replace reddit.com with teddit.net -- if you're going to Instagram, use bibliogram.art -- if you're going to Twitter, use nitter.net -- and all of these websites have alternative instances, some may unblock or block certain things, some may be faster, etc.

If you have any more questions, let me know!