I would argue they are all the same since most are based on wlroots and if wlroots doesn’t support something neither does the “increasing amount of Wayland compositors”.
While I don’t use TPM myself (I dislike being tied to a specific hardware) the way it protects you is:
Disk is protected through encryption, so you can’t remove and inject anything/hack the password.
If boot is protected/signed/authorized only, a random person can’t load an external OS and modify the disk either.
All this together would say, even if someone acquires your computer, they can’t do anything to it without an account with access, or an exploit that works before a user logs.
In a way, the attack surface can be bigger than if you simply encrypted your disk with a key and password protect that key.