Hi Archie,
Yeah I would say the normal humans like members of the Remnants will be about 28mm tall. The Haraki are about 34mm tall because they are kind of elvish in physique as they are from a low gravity world, standing next to a space marine mini the Haraki are somewhat slender compared so more realistic proportions I think, just taller due to their enviroment. The humans in armor like the SCR would be around 30-31mm tall due to the armor they wear and the Xrxn are large creatures with tenctacles and arms for appendages. Very big and bulky, hope to have art of them soon to show you guys! Thanks again.