GSM7328FS / GSM7328S 10 gig ports

There are 2 things: Yes it is absolutely possible that SFP+ ports don't support SFP or 1GE. While many devices with SFP+ slots do work with slower 1G SFP modules it can happen that they do not. The AX743 module doesn't explicitely mention SFP support. Though I have used them in the past I have never used them with 1G fiber.

However I think there is a chance that one or both ends are not running in the same port mode. Usually these module ports and some 10G ports like on the GSM7328S can run in ethernet or stacking mode. You'll have to decide if you want /can stack them (I don't know if those 2 can be stacked) or simply use the 10G ports as regular ethernet-based uplink.

Check out the the CLI manual for both switches. They should have a "show stack-port" command where you can identify the port mode of all ports that can actually be run in either of both modes. I'm certain the module slots are configurable and most of these module slots on the GSM73xx series were defaulting to stacking mode.

You can switch them between ethernet and stacking mode, however a switch has to reboot in order to actually switch the port mode. (Still valid on the current M4300 switches).