Both fish are peaceful towards other species.
Most rainbows are compatible with each other as well. Most will adapt to any kind of water - they do well in hard water for example.
The majority of Killies are not really schooling fish - indeed - they can become agressive towards other members of their own species - generally best kept as a pair. Also a bad idea to mix related Killies, Lyretails for example, espeacially if you intend to breed them - the females ín many species are indistiguishable and related species readily crossbreed to form deformed, stunted or sterile hybrids.
Some of the larger Killies, (certain Flags, Panchaxes, Gularis etc.), grow large enough to eat smaller tank mates and will happily do so.
Clams - no idea.