Manufacturers don't generally ship internal drives with any kind of partition table at all in my experience - that gets added when you do the initial install, which generally depends on what mode you booted the installer from and in turn probably on your motherboard BIOS defaults...
Correct, Dell, Lenovo, HP even enable the basic EFI(bios) menu with Secureboot enabled, granted this is a bit disabled if you get an Ubuntu/XPS model but can be enabled easily for dual booting.
This is relatively a non-issue for most orgs, you should have an imaging solution in place, if not there is Windows Hello/Autopilot, not free but easy to deploy and helps you manage and orchestrate, which is what every corporation should do with owned devices.
Machines 5yrs+ support TPM 2.0 unless you bought absolutely bargain basement prices like Dell Inspirion models from Walmart instead of Dell.com and such, but even lately those also include TPM and Secure Boot as Microsoft demanded it from it's vendors.
Building your own PC, is something that, is kinda dead in todays times though.
No manufacturer has shipped an mbr formatted drive in the last 5 years.