(Note: Anything I say could be B.S. I could be completely misunderstanding this.)
Clevis isn’t too difficult to set up - Arch Wiki documents the process really well. I’ve found it works better with dracut that mkinitcpio.
As for PCR registers (which I haven’t set up yet but should), what I can tell, it sets the hash of the boot partition and UEFI settings in the TPM PCR register so it can check for tampering on the unencrypted boot partition and refuse to give the decryption keys if it does. That way, someone can’t doctor your boot partition and say, put the keys on a flash drive - I think they’d have to totally lobotomize your machine’s hardware to do it, which only someone who has both stolen your device and has the means/budget to do that would do.
You do need to make sure these registers are updated every kernel update, or else you’ll have to manually enter the LUKS password the next boot and update it then. I’m wondering if there’s a hook I can set up where every time the boot partition is updated, it updates PCR registers.
If it doesn’t simulate a connected monitor, it looks like there are little HDMI shims that do called EDID emulators that are available for relatively cheap.