can i use thunderbolt 3 for mac to mac in migration assistant?

Yes, BUT:

There seems to be a little more to it than just connecting them together. Somebody needs to complete the Networking information, possibly including what IP addresses to use each end, or use a special mode.

If you have two computers with ThunderBolt-3 ports, you can use a genuine ThunderBolt-3 cable to connect them together. A new Network connection method will appear in System preferences > Network, and you can choose it and give it any missing information such as DNS server address. The other Mac will then connect according to this article:

Use IP over Thunderbolt to connect Mac computers - Apple Support

-OR- You could put one into Target Disk Mode. It used to be only for Firewire, but they have continued to support it using ThunderBolt.

johnkatos wrote:

can i use thunderbolt 3 for mac to mac in migration assistant?

yes

ref: https://support.apple.com/en-gb/guide/mac-help/transfer-files-mac-computers-target-disk-mode-mchlp1443/mac