uizz The adapters are not all the same. Different chips in them and the microcode to run them will produce different output. I have several adapters here and there are subtle differences here and there.
My NUC has a DP output and a HDMI output, but what most people don't know is that on newer machines the HDMI output is actually an internal DP-to-HDMI adapter.. so in my opinion it's generally better to just use a chosen adapter for DP to whatever. Older machines had native HDMI output or native VGA output.
There will be DP-to-HDMI 2.1 adapters this year. Worth trying then. 2.0's are out but might as well wait since you have a working VGA solution.
The only time the VGA solution does not work well for me on my hardware is with protected streaming video. On Amazon, for TV shows it doesn't care and will give you full resolution on VGA on 7, but for movies it cares a whole lot and will lower the resolution/bitrate. On Netflix it cares for both shows and movies and in addition, requires windows 10 to get full bitrate (this means even if you are using HDMI on 7, Netflix will limit your resolution and bitrate). Because of this (and also because my monitor is on an arm now and my vga cable was 1.5 feet or something) I started using the HDMI port on the monitor for now.
It may not be your monitor, it may just be a poor quality adapter, but there is one additional thing you can try.. there is a possibility your monitor is using a different chip internally for the DVI port than it is for the HDMI port, so in that case, what you could do is get a DVI-to-HDMI cable and try the HDMI port with your existing DVI adapter. It will work because the DVI and HDMI video signals are 100% compatible. You won't be able to use all the HDMI options with a DVI adapter on the HDMI port but the video will be there. A cable with a DVI connector at one end and HDMI on the other is cheap because it's just a cable, no chips.
Incidentally, I have an old HDMI to VGA adapter cable that strips HDCP (intentionally). I tested it out and it does work to stream movies over VGA, but the problem is that specific adapter is locked into limited range and I have no way to change it to full range since it's set in the internal hardware. I would have to use a color calibrator to compensate for the range change but I don't have a calibrator. It's another option to consider of course.