I haven't used either in ages. I'm, generally speaking, a Linux user, and Linux actually happens to make this comparatively easy. The last time I set up a Windows box for this, CRTEmudriver wasn't around. I'm told it's better, but Soft15kHz is the old standby. They're basically both registry patchers and rely on known the registry hive quirks of various drivers to redefine and add various modes.
None of these options will work prior to your OS running. The only way around that is to reprogram your video card to interlace text mode and downscale, etc. the various Windows splash screen modes. This is what the ArcadeVGA has done.