As a handler, tail harnesses are great. A harness helps create a feeling of security when wearing a tail for extended periods of time. It seems some people (especially drunks in public) have a pathological need to pull on tails and a harness will keep a pup protected and comfortable even if some jerk really tries hard to ruin your fun. A harness doesn’t feel intrusive, it can be made to be very tight and thus feel secure, it will allow your pup to relax without fear of losing their tail, and it can even be locked which not only makes your pup feel safer, it gives you greater control over your pup. Properly secured, your puppy will be free to pee without having to remove anything!
Tail harnesses also pair well with chastity cages. The harness will be secured by a cock ring which you can then (usually) put a chastity cage over the top of. With a properly sized tail, fitted harness, and appropriate chastity cage, your pup will be comfortable, safe, and easier to keep under control.
(The chastity cage is from HolyTrainer and the harness is from Mr. S Leather)