I can't say how I like my Maverick compared to the Impact, because I haven't had a lot of personal hands on time with the Impact. I do absolutely love my Maverick so far though. The Huma extra high pressure regs would definitely be the way to go, if you want to push the limits. I don't know that I'd fully trust the FX regs much past 170 bar. I think you'll start to see a bit more creep out of them past that. I just look at the factory regs for my gun as backups, should I need one in a tight. The Huma regs also come with an extra sealing disc too. I'd rather just use the Huma, and know for sure that the reg can handle the very high set points if needed, and not worry about it.
Fortunately, we can also use air guns during primitive weapons season in GA too, so I intend to put it to the test when that time rolls around! It's hard to say what I would limit myself to in the fpe department in .30 just yet. I want to do some more penetration testing etc., prior to deer season, before I make that decision. I will say a .22 making 70 fpe will probably penetrate about as far as .30 making 90-ish fpe. A small bore will always out penetrate a larger caliber at the same power, assuming all other factors are equal. I dropped a 200+lb boar with a .177 shooting at 45 fpe with 18 grain slugs, so I know placement is everything.
See here:
https://www.airgunnation.com/topic/tiny-bullet-huge-hog/page/2/?view=all#post-900941 I think the power limit will depend on where I intend to shoot the target critter. I think I would want to try and have at least 95-100 fpe on impact for a heart lung shot on a deer, but a head shot would require less. I don't want to go too far into that, since this isn't the hunting section
The real key factor there would be absolute accuracy, intimate knowledge of anatomy, and hitting exactly where you intend to. I'm pretty sure I would try and limit myself to 50 yards for the most part on a whitetail to be darn sure. If I take a shot, I intend to collect what I shot at. That's just part of being a responsible hunter, imo. Could you do it at 100 yards? Sure, but with these power levels(even 150 fpe), shot placement becomes critical. I would only try a longer shot than 50 under very special circumstances. I'm not in it to wound anything, and that's a lot of food that can go in the freezer