I tried to assign a Custom Teams policy for Guest users!!
I checked in Teams Admin Portal and tried via Powershell script, but not able to see/resolve Guest users.
Please do let me know if this is possible.
You can't assign a policy to a guest user in Teams. The only policy settings you can set for guest users are the settings you find in Teams Admin Center > Org-wide settings > Guest access
These settings applies to all guest users so you can't set so that some guest users can use video and other can't.