tthh,

There are pro's and cons to both ways as you are probably aware of. I don't shoot a loop, but have done some chron testing with brass nocks (They aren't copper). Each brass nock set reduces your speed by about 4 fps, at least according to my chrono. So with your setup you could look for about 12 fps gain by removing them

Now add a loop. This may reduce speed by 3-4 fps. Thus you would nett about 8-9 fps gain. You may be able to shoot a peep without a tube as the loop helps with peep alignment. Going from a tube peep to something like a Fletcher Mag Hunter you might realize another 8 fps. There are variables, but that is 50-20 fps. Quite substantial.

Noise level is something that you probably won't be able to detect so I wouldn't consider it an issue.

You will probably have to get a new release anyway. If your jaws have any rough spots from the brass nock sets they will chew up a loop. If you do have to get a new one then there are some that are specifically made for loop use. The head is short and the trigger closer to the head. That can counter the extra length in stretching you out. True Ball Short-n-Sweet is an example. Just try to keep your loop as short as possible. If you release jaws don't hit your nock then it's long enough. You don't need any more.

Hope this helps.