Maybe reconsider your thoughts on 4K. It's not super impressive, but extremely expensive. 1440p is the gamer's sweet spot for now and I'm quite certain it will stay like this for a couple of years. Roughly 70% of all PC gamers still game on 1080p because GPUs are so expensive.
An RTX 2060 will crush every game on 1080p and will work decently on 1440p. RTX2070 if you want more 1440p performance. RTX2080 for 1440p/144hz gaming. I really think the RTX 2060 is the first GPU in years which hits exactly the performance a lot of gamers want for a reasonable price.