A UV sterilizer is a good to use whenever you add new fish. I keep one on hand for just this purpose. The one you bought sounds fine.
I don't think that you have to worry about snails and shrimp getting mycobacteriosis from whatever species of EM (environmental mycobacteria) that fish might be carrying. My snails did not get sick.
Humans getting Fish TB is fairly rare. Just don't clean tanks when you have an open wound, sores, pin pricks, etc. Unbroken skin is an excellent barrier to EM.
Parasites are probably a bigger problem with incoming wild fish than Fish TB. Read my
article on fish diseases. Professional importers of valuable wild-caught fish often use a series of dewormers, including levamisole.
The UV will help, no matter what. It will help with bacterial infections secondary to the parasites. And if the parasites are small enough, it will kill them too.