What do you mean, alt-tabbing is slow ...why would your monitor have any effect on that?
I am considering either the XG32UCWG or the XG32UCDS ...I don't care about the dual mode functionality but I am intrigued by the true black coating of the former although that's not necessarily a major factor, just interested in it, but I use mine in a room with low lighting and behind display lights anyway so reflections are not an issue.
I've been thinking I would like to change to a 4K OLED, currently using an Alienware AW3423DW, recently I played a few games on my secondary display, a 28 inch 4K Samsung Odyssey G7 IPS and I was quite taken at how sharp the textures were in farm sim ...the colours aren't as a good obviously, the blacks are not black and HDR is ..well it isn't, but the sharpness and detail ..wow ...so I'm thinking it's time to combine all of that, OLED and all it's talents and 4K, I have the power, have done for a good while I use a 4080 Super.
I've been going backwards and forwards on weather I want a 27 inch or a 32 inch display, I think 32 inch really, I know it will be very slightly less sharp than the 27 but I use 125% scaling on my 28" IPS in Windows, so I should think I'll be comfortable at 100% scaling on a 32", which is ideal, also I can move it backwards a bit as I have an 80CM deep desk so no worries there, it should be a bit more immersive too. I do want one of the Asus models with the motion sensor, that's a brilliant addition and I can see a real benefit in having that for the way I use my PC.