I have had a 'contact darkroom' such as you mention. I have used both Azo and POP. If you have nice negatives, POP is an easy way to go. Both Azo and POP need fixing and toning and washing. POP is easily exposed using sunlight through a window and, since it is a POP, you see what you get. It is also self masking, which means darker areas, as they print out, block additional light reaching the area in relation to the exposure already received. POP also has an excellent glossy surface, is heavier and is easier to handle than Azo.

On the other hand, I have personally had some quality issues with POP. Azo seems indestructible.

I imagine that water treatment of POP is safer than paper developers used on Azo. Both papers still need fixing and toning so that aspect is the same. I understand Begger also has a contact printing paper but have not used it.

As a much different aside, cyanotype is also very easy to use as contact printing method, requires no developer, no fixer and no toning except maybe tea or coffee. And the chemicals are 'safer' than many photographic chemicals.

The previous posting about using mylar is a good idea with POP. Otherwise, I understand that the excess silver on the POP can affect your negative. But I would use the same precaution in any contact printing method. I have never suffered the damage becasue I have always shielded my negs, but it seems reasonable.

Cheers, Richard