Most of the fish you cite won't make very good companions for Malawis, in part because they have very different water requirements. Malawis also tend to be pretty aggressive, making it hard to pair them with non-african fish. It's not impossible, but it is not easy to find non-african tankmates.
I've heard of loaches being kept with africans, but I don't think the water requirments for Rift Lake cichlids (very hard, high pH) are optimal for clown loaches. Most gouramies will get beat up pretty bad, and a betta would not last long either. Don't know about severums... not sure they'd tolerate the water parameters, either, but I confess I don't know much about them.
A lot of us keep Rift Lake-only tanks just for this reason. It's easier to find compatible species if you look at those that actually live together in the wild. If you want suggestions in that realm, I sure we could help you out.
HTH,
Jim