I don't think ACT (unlike MPC) have an explicit use case for different embodiment. Or what do you mean by two different instances? Two different tasks /arm/robots? Their recent work (Octo policy or something) wasn't even that convincing in that evaluation.
But as you're a fellow Robot Learning (BC/LfD I'm assuming) practitioner, in the field of BC (Not IRL) what have been the more robust method for your case?