jeeez that is some MTS you have there. if my house had the space id be all over craigslist buying tanks. i still say either planted discus with some schoolers or an oscar pair for the 120
for the 75 id go for a lake malawi cichlid setup
or a discus setup for the 75 if you went with the oscars for the 120. i guess those are my favorite fish and tank types.. Oscar minimalist tanks, discus heavily planted, and lake malawi cichlid setups. either that or id go heavily all green planted in the 120 and fill it with a bunch of small schoolers like Harlequin Rasboras.
paludariums are awesome too, i want one. when i finally have it im planning a kind of trippy enchanted alice in wonderlandish type paludarium- discus if possible w/ some small colorful schoolers like cardinals, or some eerie looking fish like loaches, cats, ropefish, ancient fish, etc.. a big tree stump going from in the water to above the water line(maybe instead of reg driftwood id use a "contorted hazelnut" tree stump w branches), funky plants(weird shaped, cool colored, etc), floating plants with dark foresty looking planted areas, some cool rocks and aquascaping and some funky dim lighting, maybe with a purplish/blacklight tint?.. for above water id have some treefrogs(the lazy bright green red-eye kind, if possible, still need to do my research) or this BIG huge albino fat "buddha frog"(what i call it) that i saw at a LPS.. dont even see how this thing would jump if it wanted to, or a snake or 2 if i could keep them from going into the water.. and id keep the same theme as with the under water part of the paludarium for the terrarium part. im thinking of making the land area with greatstufffoam, coming from in the water and sloping up to until the land starts, so that the underwater area is maximized.
my bad for completely rambling, its just all the options that you have
hmmm, you have many options.. and many pages of responses. i hope i catch it when you choose what youre gonna do