Because of an underpowered GPU, is it worth it to get a tandom 4K oLED?

I'm not an eSports game player, just a mostly-single player gamer. I want OLED so I'm looking at 4K + 1080p tandem because my RTX 5070 can't do 4K with all the bells n' whistles only at 1080.

Do I need a tandem panel (I don't care about the boosted refresh in 1080) to game in 1080 or will its scaling (done through the GPU I assume) be fine on a non-tandem panel?

I know 1080p image on 1440p panel looks worse and the common wisdom is because 4K is exactly 4x it should scale with better quality? Do I need the extra cost of tandem even?

Edit: I had 4K before on a 27" monitor and my vision is too bad to see text at 1:1 but I want 4K again for the window density in productivity. I don't like curved so it has to be flat. If there were some 4K screen size between 32 and 42 I'm not aware of any panels. On 4K I will probably run 125% or 150% desktop scaling.

Ryzen 7 5700X and DDR4-3200 32GB.

It's mini ITX SFF so I can't get a bigger PSU in the NR200P case.

Looking at LG Odyssey G8 G80SH unless someone can suggest another comparable model. $999CAD on sale, or hoping it goes to $899 Canadian by Black Friday in Nov.