[Wintermute]

PLO8 is a goldmine if you have the right mindset, and it sounds like you do. 20 BB/100 may not be sustainable at higher levels where the blunders may not be as severe, but 10-15 BB/100 is certainly possible, and I'm sure there are players who hit 20 at even the highest levels.

As for the skill, I haven't played the $50 or $25 so I don't have a good sense for comparison... however, from $200 to $600, the games are an utter joke, I would imagine they are comparable to the $25 games only with a little more aggression. (In fact, I'd say that's the biggest difference in the levels--as you go higher, the play gets more aggressive... you won't see as much less-than-the-pot betting.) The $100 game is a bizarre mix in my opinion (this is just over a few hundred hands though)... this seems to be the level where risk-averse smart players prefer to stick, so you get a handful of rocks, but then there are players who are truly the stupidest players I've ever encountered. I'd recommend datamining that level with PTO and identifying the players who know what they're doing, and then eat the rest alive.
At $1000 and $2000, the play gets markedly better, but both are still beatable.

In terms of beatablity, I'd rank the games (most beatable first):

600
400
200
1000/2000

Probably stick 100 around the 200/400 point or so I guess, just haven't played enough hands there to say for sure.

If you're having trouble finding a game at $50 & you have the $2k or so you'd probably want for the $100 game, I'd suggest just jumping to $100. From the sound of it you'll have no trouble beating the game.