So I came back to BFA last weekend and have a ton of questions that pop up and communication in game is ridiculously bad. Asking questions is like pulling teeth, so here we go.

1. Are the communities cross server?

2. Any add-ons for finding groups for wq's? I can't get my WQ group finder to work, tried updating/re-installing and everything.

Afaik the only cross realm technology being used is for battlegrounds. They're also using layering here in the very beginning of the launch, which works like sharding from retail (but it's not cross realm).

Q: Will there be Cross Realm Battlegrounds when those go live?
A: Cross-realm battlegrounds were a feature of 1.12 and are important for matchmaking, so you’ll be seeing cross-realm battlegrounds in WoW Classic when Battlegrounds are introduced in Phase 3 of the content roll-out plan.
Source: https://worldofwarcraft.com/en-us/news/23090136/world-of-warcraft-classic-faq-what-you-need-to-know

I don't play Classic myself so I'm not 100% sure about your second question, however, I know they added restrictions to the Classic addon API to avoid addons such as these.
Source: https://eu.forums.blizzard.com/en/wow/t/classic-lfg/72495/475

To clarify, these questions are for retail, not classic.

Yes, communities are cross realm, you can invite other people to your raid or group in general, as long as they belong to the same faction as you