Hot air re-ingestion was less of a factor when I had my "BLOWer" Titan X Pascal in the rig.
Im running a 5ghz OC on the 8700k. But temps have not been an issue for the CPU or GPU....however, I do have to run the 2080ti at 100% fans to keep 2000mhz & temps under 80c
Yeah, builds like yours are why blower cards exist. I see no need for you to do watercooling (nevermind the space that takes) as long as you get some serious air movement going in the case. Perhaps a 120mm fan blowing on your card and an add'l fan helping pull exhaust out by the external slots. Not like you have room to mount them...ha.
If I were you, I'd seriously consider buying a blower 2080 Ti. Even if they're the jankiest ones. It will help your performance.
Also, you could get an AIO cooler if you have room and watercool that CPU to add more airflow capability.