Hop up should be turned down to stop the "BB lift" at the end. Tune it right at the start of a game cause humidity and air pressure can supposedly affect your ideal hop up setting for the day. Turn it all the way off then shoot, turn it up until you get the straightest distance and a little bit of "lift" and then turn it back down a little to get your maximum effective range.

You're going to want to probably .25's or .28's if you're playing outdoor for more predictable shots even if you slow down the BB, it will get tighter groupings and better brush penetration.

Also if your shop told you to use .25's to slow down the speed then I would not use them at all (they don't seem to know the difference between velocity and energy). Go to another shop or find a new gundoc.

You could probably downgrade the spring, M120 is probably what you want to be aiming for. Otherwise a 1J spring (I believe this corresponds to a standard M100 spring) will do the trick and you should be able to play CQB too.

I would either downgrade your spring to one within the 1 Joule (328fps @ 0.20g BB) range, or swap the inner barrel to a straight bore barrel.

A straight bore barrel at 380fps will have greater effective range than a Twist barrel at 328fps, however, the effective range that the Twist barrel has will be straighter and more predictable than 380fps with a straight bore for the effective range. Beyond that, the 380fps straight bore setup will outshoot the Twist barrel.

Figure out what you prefer... a straight predictable flight, or a greater effective range. In my tests, my M14 shot 380fps with the Twist barrel and the flight path was very unpredictable. I would not recommend using a Twist barrel at that velocity.

With the Twist barrel, hop up is set as you normally would. Once you go too high, the BB starts to do crazy things.

I've got a Twist barrel in my M14 right now... It shoots at about 400fps with .2s. I use .28s and it shoots at 330ish with em... my groupings with the twist barrel are amazing... I also get a range of about 50m with very nice accuracy...

That does not reflect my experience with a Twist barrel in my M14 or any other high powered airsoft gun. You may have a magics setup. Don't touch anything in it... keep it the way it is!

Absolutely!
I originally thought that it would affect the shot like crazy but after I gamed it and had some nice kills at pretty long range and some quick close range snap shots, I found out it's dead on. I put a few rounds on target in my back yard with it just to see after that game and sure enough... consistent groupings.

*EDIT* Yep just went and tested it in my backyard again... It's got a grouping of a couple Centimeters at roughly 25m (length of my backyard.)