There's still a "default", at least on my PC.

But yeah, using the uefi works fine to choose between windows and linux, even if you only have a single /efi partition (I use efistub for linux, not a dedicated bootloader).

If you add custom boot options, they won't be removed after a windows install, it only adds itself to the list and sets itself as the first in line. Afterwards, it doesn't seem to touch that anymore, but YMMV with "big" updates.