I have a 29g tank low tech planted with
5x Zebra danio
4x Neon Tetra
1x GBR
1x BN Pleco
(I'll more than likely move up the number of schoolers to no more than 8)
I think sticking with a school of cories and another school then getting a centerpiece fish works really well with a 29g although I'm no expert at stocking tanks this is something I see work often.