The integrated IAT's are nice, personally I like to keep it separate as those are known to fail (and a lot cheaper to replace as a separate unit). If you're installing a kit it probably has the IAT provisions already so you'll end up needing to plug it and also go with a different pigtail for the MAF itself. So that sounds like more hassle to me.
You're right that all vacuum-operated fuel pressure regulators will "reference boost" to a degree. Noobz is right, that term usually doesn't mean too much outside of the FMU world. Theoretically however much boost you make will increase your pressure the same amount to overcome the resistance the fuel injectors now feel (and likewise when you're drawing vacuum decreasing the pressure at the rail). Took me a while to realize vacuum is inHG while boost is typically PSI, so up from 0 (at boost) you'll see 1:1, down from 0 (at vacuum) you'll see a smaller pressure decrease for each inHG of vacuum (but still 1:1 when using psi for both measures).
Personally I'd get a good quality adjustable -- while the diaphragm in the stock unit can probably handle up to 10psi ok, I think it's a pretty weak little unit and if you pop the diaphragm at full boost you'll see a sudden drop in fuel pressure which could be catastrophic. You're right that you shouldn't ever need to use it (though I'm using it to cheat my injectors up a size by running a higher pressure at the rail which you could do too once you realize even 10psi isn't enough! -- FYI your signature says 30lb injectors, that's not going to be nearly enough for 10psi... I'm cheating my 36lb'ers Bosch 4-pin injectors up to 42 running at 55psi which is just about right for 10psi.).
When you get around to tuning, you're welcomed to my tune. 42lb injectors, 10psi, PRO-M MAF, otherwise largely stock. You'll want to tune for up to 200% load and have full-boost AFR's in the high 10's or low 11's. And lots of other stuff you're welcomed to.