Get more than 3 cories, they are social fish, so a group of 6 or more is best. You could get 6 panda cories, bandit cories, albino cories, or trilineatus cories. And still have room for a few ottos.
If you get the kuhli loaches, you have room for 4-6. They aren't very big at all...get about 4 inches, but they are pretty skinny.
For a small pleco, what about a clown pleco? They aren't great algae eaters, but they stay pretty small. A bristlenose would be ok, they can get 4-5 inches though.