I am working in a software (not really a game) that has to run in a web browser in all sort of devices so every little performance boost is relevant.
I am also quite inexperienced. In this software you should be able, as a first person player, to grab 3D items, move them around and then drop them. For now the implementation I did keeps all those items as StaticBody3D objects since they don't need any sort of physics, not even when they are moved around, and they only need to behave realistically with physics when the player drops them and the object needs to fall to the floor or on top of other objects and "settle" there.

A script converts the items to RigidBody3D only while they are being dropped, and converts them back to StaticBody3D once they settled.

A bit afterwards I found out that you can use the Freeze and FreezeMode properties to remove physics from a RigidBody3D, basically behaving as StaticBody3D nodes.

Does anybody know if the performance would be equivalent? I will have hundreds of these objects potentially running in the same scene.

3 months later

Seems like the kinda thing you'd need to find out by stress-testing. Have a scene with a bunch of static bodies vs a scene with a bunch of rigidbodies and compare performance. Then a scene moving a bunch of static bodies vs a scene moving a bunch of frozen rigidbodies. I don't know if anyone has already done this in Godot. If you ask in the # physics channel on the official discord server, someone there might know.

It's unfortunate that godot-jolt doesn't support web, or switching to that would take care of all of your performance worries.