A few people including VR Flight Sim Guy are recommending the 3090 because its got loads more VRAM but all that extra VRAM is only useful if its actually used and you need to pair it with a really good CPU to get the most out of it. I’ve got a RTX 3080 and the VRAM is really underused because I’m running it with an i7 7700, which is an older processor.
I would have thought your Ryzen 5 5600 would be better paired with an RTX 3080, 3070 or 3060ti.