Hi, bg!
Recently found and installed http://www.tesnexus.com/downloads/file.php?id=25524 mod and tried it - looks really good but I don't know how it works with RBP.
Should I expect any problems?
Races are not in tune with RBP, otherwise none. You can easily bring them in tune with RBP - there's a part in the readme describing how to

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If yes, would you consider integrating it with RBP in case of future updates if you think it's worth it?
I will not include variants of existing races

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I recently noticed that my level 15 Atronach Hidden elf only has 102 magicka when wearing nothing. I can't see anything in the magic effects page that would cause this, actually the fortify magicka blessings for birthsign/race alone is 420.
You're using a mod changing various gamesettings and recalculating your magicka through scripts.
You can try to disable the mod, run the stat fix of UOP, then use the update command. Hopefully it will work. Otherwise it has to be setav'd correctly.
Putting it bluntly: Some character leveling mods have become overlords - instead of just taking care of attributes and skills, they force their own Magicka and Health formulas on the player, often based on Vanilla or something similar to Vanilla, blissfully unaware that some players use alternate formulas. I cannot do anything about it. My personal choice is SPAM - unintrusive, and taking only care about what's written on the tin.