I wouldnt put any plec in there.
Stick to dwarf catfish like ottos to combat algae. The ABSOLUTE minimum for any plec should be 20 gallons. As for a common plec, well you obviously haven't done ANY research at all otherwise within 2 minutes you would know that they can easily reach 14" and aren't suited for anything under 40 gallons at all.
The 5 peppered and 5 dwarf corys would be fine. Get 3 otto catfish and you will be sorted. You could then maybe have a group of tetras or some other group of shoaling fish to fill up the rest of the tank.
Ben