How to create two groups? Only one has hw offloading.

I guess you cannot have achieve that, unlike with old master-port configuration. You need to set up isolation profiles and/or vlans to create virtually two switches.

The old configuration also did not allow two master-ports.

Does anyone know if it is possible to create the isolation profiles in Router OS? I still don't see those menu items available. I have no interest in using SWOS. Since its adoption, I don't see this switch as a very effective replacement for the CRS226 as we use it.

two groups? like two independent L2 domains?
use bridge VLANs.