J-pouches can stay in unused, though some people develop diversion pouchitis and decide to have it removed. A loop ileostomy is also frequently a nuisance, and an end-ileostomy is a better long-term option for most people.

Is there a higher output with a loop than and end Ileostomy?

You can search for and read many dozens of posts here about various experiences with loop ileostomies. The majority that I've seen are negative, in various ways, though some folks do fine (and we have to keep in mind here that folks who are doing fine tend not to post about it, or even visit the J-pouch forum).

I personally would not suggest a unused J-pouch to stay intact if you are not using it, temporary is fine but not for years on end. I would either get connected or opt to have the J-pouch taken out.

I have an end ileostomy and the output has slowed down significantly! I am even less dehydrated than before. I would suggest an end ileostomy for sure.

If you have any questions, feel free to pm me anytime.