Depends on what you like. I have worn those in uniform for a long time. Also, just remember most people have field boots and garrison boots. When you are in the field, you unblouse your boots.

I personally like the regular just because there are not a lot of times that you will really need the goretex in training. If your feet are getting wet in training, then your whole body is also wet because you are either getting spayed with a hose or going through a creek.

Yes as long as they fall within AFI 36-2903.