Yo-yo loaches are active and will go throughout the entire tank.
Skunks are tougher and don't usually bother other fish often, but they are also a bit more shy and stick to the bottom more than yo-yos.
I'd say upgrade your tank so you can have more tiger barbs and some loaches. If you go with yo-yos I'd say get either 1 or 3+. With Skunks I noticed no difference in having 1, 2 or 3 in my tank (as far as behavior but there will always be one slightly more dominant one).