Probably the most given advice around here is to ditch Digilink.
HOWEVER given that you have the Burl we can't tell you to get a better interface
I would definitely go for the HD Native Thunderbolt in this case. Simple solution to keep you working exactly as you're used to. I don't know much about Soundgrid but if you're not running a Soundgrid server I don't see the point.
There are reports of folks here happily running sessions on the Mac Studio internal drive. External SSD'S will be fine as well and they don't have to be Thunderbolt. NVME drives are much faster than the old standard SATA drives so look for an enclosure you can use for that.