This topic has two useful data points for legacy GPU hardware
Post 86 shows most of what happens when mhwd installs 470xx driver to replace Live ISO FREE driver
warning: libxnvctrl-470xx-470.256.02-1 is up to date -- skipping`
shows that the legacy version of libxnvcontrol is already installed
Post 93 shows why Live ISO NON-FREE driver cannot be replaced
libxnvctrl-470xx-470.256.02-1 and libxnvctrl-580.82.09-1 are in conflict
NON-FREE installs latest version of libxnvcontrol that cannot be replaced by legacy version
If user cannot press Y to replace package, pacman is probably using --no-confirm option.
If mhwd was hacked to remove --no-confirm option I suspect pacman will request replacement of more packages and might fail. mhwd script might also fail to reconfigure or create system files
it could be a very long and winding road to install legacy driver on a NON-FREE install without using mhwd - more downtime than re-installing with FREE