My angels spawn in my 75 every couple weeks... they chase the other fish away from their filter inlet, but I haven't seen any actual damage. I would assume a 90 would be even better.
I also keep a large snakeskin Gourami in my tank, without any problems between him and the Angels. Big Angels WILL eat your neons though, jumbo or not. I had a dwarf gourami in the tank for a year also, until he died last week. Again, I never saw any aggression between him and the angels or the big gourami.
Loaches aren't really algea eaters... they're more scavanger types, like cories... they'll eat food crumbs that fall to the bottom and keep your substrate clean, but they won't make a dent in any algea. Besides, if you're going with a planted tank you should have some kind of carbon injection, and that will go a long way to combating algea. Beyond that ottos or rubberlip plecos will go with your fish and will keep your tank looking pristine. I do love loaches though... everytime I've went to pick some up though they were in terrible shape at the fish store

Just don't expect them to control algea.
A beta won't go with angels or gouramis.
I agree with the comments about the tetras... if you want a schooling fish, a small school of rainbows or one of the larger tetra species would work well, but neons will always be bite-sized (as will cardinals, danios, glo-lights, and the like)