Have you executed
tpm.msc in Start > Run? Check if it's not already enabled before going into the BIOS.
I looked at the HP website and
TPM 1.2 is supported on your Omen Pro. Although you should be able to upgrade to Win11 since 1.2 is the minimum, the CPU is
not supported. My mobo supports TPM 2.0 but my 6600K is not supported. So we're **** out of luck (for now hopefully).
As for your BIOS situation, generally UEFI mode is recommended since it introduces some security features and has better boot times especially with an SSD. Honestly, if you use Win10 or any modern Linux distro, there's no reason to use legacy mode. Also, UEFI has a sexier user interface.