Disappointed ex-Reddit user after the APIcalypse - starter pack

I used to browse Reddit 90+% of the time from my phone through the RiF app, so after June 30th, here is what I did and what I recommend as a starter pack for others in the same situation:

• Create account on lemmy.world, so the browser part is covered
• Search for the information on which app provides the closest to the RiF (Apollo, etc.) experience
• Instal Liftoff and be happy - it is just like RiF :-) (for Apollo and others, it could be different - find your own favorite!)
• Dial back dramatically on using Reddit at all. I only load 4 subs in my phone's browser, because I did not find the Lemmy / Fediverse alternatives yet
• Constantly look for the communities to replace the subreddits you are still visiting
• OPTIONAL - once or twice a week, look at /r/pics and /r/videos and laugh at the creativity of the still ongoing protest :-)

So that is where I am right now, posting this via the web browser on the lemmy.world site, by pressing "create a post". Seems easy enough for now, but I find it a bit confusing that other people can post from Mastodon and other Lemmy instances... Do they see the same communities I do? Do I see all Lemmy communities if I use lemmy.world....? So many questions, but it's exciting to explore this brand new structure.

Even after reading the Fediverse and ActivityPub articles on Wikipedia my head is spinning, and I don't really understand how everything fits / works together, but here I am! An ex(-ish) Redditor after the APIcalypse, looking for cool new communities, and excited about the future that the Fediverse can bring!

(I'm willing to learn! Someone please link me a FAQ where I can find the answers to my questions :-) )