Hey I've been playing level 50 on the EU realms for a few months now, so I can try to answer your questions and post a little bracket review / state of the bracket report.
First of all pretty much none of the prominent members of this bracket use xpoff or any other forums to communicate. There are in-game communities on both factions that serve as the main hubs. There is almost no cross-faction communication either. You will also find that the factions really hate each other for whatever reason.
I don't have any experience making my own gold in wow, so I hope someone else can answer this better... Making ~300k gold a month seems pretty difficult/time consuming but maybe not, idk.
Starting with raids:
I play alliance so I'm speaking from that pov. Most alliance players are pveers. They run heroic nyalotha consistently every week. They rarely make it past Xanesh though, so keep that in mind. They also sometimes run mythic and kill a few bosses. Also, in case you're actually interested in pve, keep in mind these raids are not strictly level 50 - They invite as many 60s as they can find (though Nyalotha is pretty unpopular because the transmogs suck).
The horde also run weekly nyalotha, though I know less about how it works for them. My understanding is that it's pretty much the same thing. The horde side has most of the actual pvp players in this bracket.
Side note: on november 3rd 9.1.5 comes out and might change how difficult Nyalotha is (I'm not sure):
As for battlegrounds:
Honestly the quality of games and queue times are in a pretty shit state. Since I've joined the bracket (approx. 2 months ago) I've heard constant promises of "things will get better soon", "x players are coming back next week/soon", etc from various other twinks.
None of this has happened yet, and you should assume it won't.
Battlegrounds pop consistently in the afternoons and evenings (~15:00 - 23:00) once every hour or so. Sometimes slower, especially in the earlier hours of the afternoon, and sometimes faster (down to 15 minute queues sometimes) in the late hours of the evening.
However, most of the players in these battlegrounds are not twinks. And most of those who are twinks are not pvp players, at all.
The 50 bracket is positioned uniquely as a sponge for a lot of new / returning players who haven't bought Shadowlands yet. This is most of the bracket. There is a sub-community of actual twinks (like me) who have chosen level 50 specifically, but most of these players are on horde, which creates a huge imbalance of factions when all the twinks are queuing simultaneously (rarely happens).
Right now the reality is: 70% of the games you get into are either completely stomped by alliance because horde didn't have enough twinks, or vice versa. ~30% of the games have roughly equal numbers of twinks (usually 3v3 or 4v4 with the rest being random 50s) and those games are fun.
Skirmishes:
50 twinks never queue skirmishes. I don't know why. I've been queuing almost every day and pretty much never run into anything except random 50s with no gear.
You've probably, like me, been reading some of the posts in the 50 section here on xpoff, which are mostly written by the american 50 players. The culture around gear is WAY different (much more casual) on the european side. In general the bracket seems much more popular in america (that's the impression I get from reading here on xpoff).
So basically, if you have gear from visions (ilvl 125) mixed with some Nyalotha heroic gear, you're already outgearing 90% of the bracket. People don't take character building very seriously here. On a side note most of the playerbase is very uninformed about itemization in general. Humans generally don't run rele trinkets. People generally build too little vers. A lot of people have no pvp trinket equipped at all.
If you care at all about itemization and character building, and have a basic understanding of stats, you'll be miles ahead of the average player in this bracket already.
It took me about a month of visions + joining community raids to get to a gear level that is more than good enough. I can still improve it, but at this level I don't feel like gear is holding me back anymore.
I hope some of this info helped
Let me know if you have more questions or whatever