I can confirm that Eve Spectrum can support custom resolutions and refresh rates missing from EDID.
Large Vertical Totals (Quick Frame Transport, aka 60Hz modes that transmit in 1/144sec over the cable), such as Vertical Total ~3500, is supported by the Eve Spectrum for 1080p signals.
MT, you should test Quick Frame Transport for lag-reduced 1080p/60 integer scaling.
I have some custom numbers for you to enter in ToastyX or NVIDIA Custom Resolution, if you would like to test lag-reduced 1080p modes, more than 50% less lag for screen bottom edge, since it’s a 60Hz refresh cycle transmitted over the cable in 1/144sec, and painted onto the panel in 1/144sec, so your eyes sees the low-Hz refresh cycle sooner.
I’ve often created odd refresh rates like 65.3Hz and 128Hz on Spectrum and it works fine, provided you derive from a working higher-Hz mode and edit the Hz downwards without modifying other numbers in Custom Resolution Utility.
There are some ambiguities like scaling behaviors (already known in this thread), but the modes will display.
I have confirmed Eve Spectrum supports Quick Frame Transport, but sometimes I have to create it in both ToastyX and NVIDIA, for it to work ‘properly’ (because of the need to override NVIDIA scaling behaviors)