Ideas For A Subtropical Tank?

[Aquarium]

I'm setting up a 20-gallon high tank and, due to its placement near an exterior door, am trying to come up with a subtropical stock plan that I hope will not seem boring compared to what I was planning for a tropical tank...we like the Bolivian Rams due to their appearance and personality/swimming style, for instance.

I like Red & White Ryukin Goldfish, but one plus a few WCMM probably wouldn't be a good idea...and goldfish are dumb--I would prefer a smarter focal fish.

1st idea: 2-3 American Flag Fish, school of WCMM, and another fish or 2 (peaceful fish tank idea)

2nd idea: Paradise Fish, 3 Rosy barbs, and ? (semi-aggresive/larger fish tank idea)

Thanks for any ideas!

 

[Aquarium]

Okay, so as I'm doing additional research into subtropical fish, I'm seeing conflicting information on the supposed aggression of the Paradise Fish, as well as the supposed peacefulness of the American Flag fish....but it does seem like the Paradise Fish is my best bet for a smart, colorful subtropical fish...so anybody have a Paradise Fish in a community tank?