Arranging my two Aquariums!?

I would leave the loaches, redtail, and gouramis in the 75. Maybe a couple of the plecos, too. Add the angels, rams, and other plecos into the 100. You can then add to the 100 with a school of something nice, like cardinal or rummynose tetras. Go with a large-ish number, like 20-30, for the best behavior and health on these guys.