Sorry, I tired to make it simple, but basically, any legacy adapter like DVI will always be priority #1 with every thing else following afterwards.
And with the other types (DP and HDMI) going from left to right on the plugs is higher to lower priority.
There is no way to change which screen the BIOS shows up on unless you hack the BIOS of the graphics card and change it, (assuming it wasn't hard coded in) or you get a DP/HDMI to DVI adapter so that you can plug the DVI monitor into one of the DP/HDMI ports to the right of the other monitor that is plugged in (making sure the other monitor is the the left of any other monitor in the lineup of plugs)
As stated by someone else though, this is only for the boot up/splash screen of the BIOS, after that, in Windows, you can set which monitor is primary so that your main task bar and login screen etc. are all on the monitor you want them to be.
It's just going to be the startup that shows on the legacy connection first when booting the PC.