i tried using a 42" tv with my PC. it wasn't great. 42" is far too big to have sitting on my desk. i'd only use a display that size if i was siting further away. sometimes i hook my PC up to my 55" tv but that's fine cause i'm on the other side of the room.
for a desktop monitor i wouldn't be going over 32". i had a 32" monitor too and even that felt big but i could've dealt with it. i'm on a 27" monitor now and i think it's the perfect size. i'm not feeling any need for a bigger display. as for refresh rate my monitor is also 165hz but i wouldn't mind going down to 120hz. i have it at 144hz cause i don't feel 165hz is that big a difference. i also wouldn't mind dropping down to 120hz cause it's only 25hz. 120hz is still perfectly enjoyable. both my TVs are 120hz and playing PC games on it is great.
i'd love a 27-32" OLED display. if LG offered one I'd go for it even if it is only 120hz but 42" is too big.