Welcome! 
At this point your best bet is to wait a few months and see which devices add matter compatibility.
Both smartthings and Google will have some Matter compatibility, but we won’t know exactly which devices, and which features until all the manufacturers are caught up, which may take until the end of the year. But there should be quite a few more devices which work readily with both by then.
You can read more about Matter from a SmartThings perspective in the following thread:
Matter - smart home connectivity standard (formerly Project CHIP)
Until then, it comes down to the first rule of home automation: “the model number matters.“ If you can list the specific brand/model of a device that you would like to work with, we can make some more suggestions.