Well, all solved. Come to find out I was also having another unrelated issue (with the screen not wanting to hold a graphic setting and defaulting to a energy saver mode, ugh). Samsung suggested trying another HDMI input other than "1". I opted for the "2" input and while at it decided to see if SH4 would even launch. It did. Then W10 automatically ran a compatibility something-or-another and SH4 is back but now in 3840x2160 glory. Problem is now it looks really dated on the bigger screen graphics-wise, but anxious to mod and try it nonetheless!
So HDMI input number 2. Go figure. Obviously for whatever reason the HDMI input on this screen does not like my PC - or vice versa.
Thanks again lads and lassies!