Windows - both on separate physical NVME SSD drives).

rEFInd is a boot manager that allows to execute UEFI boot loaders. It looks much nicer than old-school GRUB menu:

rEFInd menu

You can customize it with themes and icons. Just take a look at the possibilities.

Things to remember

Make rEFInd default

After installation of rEFInd (sudo apt install refind), you need to run sudo refind-mkdefault to ensure rEFInd will be used by the default.

You’re good to go once you’ll see:

rEFInd is already the first entry

Configure rEFInd

Check /boot/efi/EFI/refind/refind.conf for configuration options.

You can e.g. hide some of the unused menu entries or change the screen resolution (resolution max).

Running kernel directly

If you want to skip GRUB as a boot loader, you can choose vmlinuz from the menu and go straight to the kernel booting.