Earlier quoted context omitted.
My Lenovo from last year still has non-soldered NVMe drives. I would probably just install Windows on a separate partition and set it to boot to that, then install a few games and set my Chrome homepage. I bet CBP won't be mucking around with bootloader settings looking for Linux, and even so it would be pretty trivial to just remove GRUB from the EFI partition for the travel days.
This is something no on discusses but I've wondered heavily- GRUB can be made to not show a menu and then boot up Windows automatically, in like a second or two with no one the wiser. [There is an obnoxious welcome to grub message that pops up now but I see a public project out there that solves this very easily called GRUB shusher] I don't know if other bootloaders outside GRUB have a silent/hidden start option, as…
I left a comment about Veracrypt offering the Hidden OS feature, with two passwords - one for the dummy OS and one for the real OS. However it doesn't seem to be supported anymore on Windows 11 or modern hardware, the option is greyed out on my laptop with no explanation.