Sunspark Thats pretty much what I did for the driver I found on the Dell site. I'll try the machine out later today as my headache has subsided somewhat today. Can always try the one you linked but It'll probably be the same, the Dell one I found was just a bundled download for another machine that has the same hardware - although again it gave me the choice to select what adapter I had when installing.
ravipra I would agree that i7 machines are normally 'better' but I dont think this has anything to do with RAM speed, unless its integrated graphics RAM speed. - however my work t540 has an Intel i5 4210m with Intel HD4600 graphics and DDR3 1600mhz (guessing) RAM and is totally fine on its 720p TN screen and my external IPS ultrawide and TN FHD screens.
The DELL 5590 has a UHD620 and I'm guessing DDR4 2133 / 2400mhz RAM and is bad.
Macbook Pro 2015 has 1866mhz DDR3 and is BAD on its intel iris whatever graphics. (in OSX / Windows 10 and several Linux installations on built in retina screen at all scaling settings and external screens also bad)
T460 has an intel i5 6300u and 12GB of DDR4, however 4GB are integrated. I could try removing the 8gb module after the new driver test as I dont know what speed its running at. Probably 2133mhz.
My personal i7 machine has 2133mhz DDR4 with HD530 and is fine, but it also has a GTX1060 with 6gb DDR5(?) but this isnt in use all the time.
I've also got an older Lenovo with a 3rd gen i7 with 6GB 1000/1600mhz(?) DDR3 RAM and a GTX620 2GB and this is fine on its 720p TN screen and my externals, although I hardly use it as its got hardware problems.
I've also got access to an older AMD laptop that is practically a potato with a screen attached, this is very low powered and is totally fine for the few times I've used it before giving up because its so slow - no idea on the full specs but its about 5 years old and has 4GB ram and a quad core cpu.
However all my slower stuff is older and I think everyone agrees that monitor 'tech' changed around 2010-2015ish when people started getting eyestrain / headache problems even with flicker free screens.
But still you may be on to something as dedicated graphics memory is usually always faster than RAM and my machines with dedicated graphics memory (faster) are ok for me, but older. I'll have to dig out the full specs.