Old problem. Can't set 120\144 Hz with HD 7970 and LG 24gm77-b using dvi-d, hdmi, d-sub on windows 10 and latest amd drivers and monitor (only one).
Drivers said that monitor support 120 Hz (not 144), but no option in windows.
Also if someone successfully using 120\144 on 720p\1080p just open this tab and do screen (that will be what I need).
Wut!? It work's. I get out card to check if there is some switches, set back, start system, check propertys - 120\144 1920x1080.
Guess was need some like total restart (like power off, not just restart (seems restart in windows 10 is not full restart or idk)).
Connected by in upper card slot DVI-I by DVI-D double cabel. (probably, 1% that I miss this combination. Sry, but I too tired to check it. If someone will be need in it - update thread).