The case and lack of airflow is the problem, not the coolers. KAC I already proved to you the FTW3 cooler operates just fine.
As for the ITX case .. that's simply not enough cooling and poor design. The GPU is super starved for air, and the only air you have coming into the case is hot used radiator air, and that's feeding your GPU, which is then heating it up further and recycling it. I'm not sure why you can't fit a rear fan as exhaust judging by the pics of the Neo Mini V2. I would actually put a fan on the rear and set it as intake, and take off all the PCIE slot covers. Let the positive air pressure force the air out on its own. You need fresh air into the case, and right now you're cooling your RAM, mobo VRM, and GPU with already warm air. Removing the side panel is allowing the GPU to pull in cool air, which is why temps drop.
Beyond that, I would highly recommend grabbing a new case and transplanting everything. The specs are nice, but whoever thought to smash any high powered CPU into a Mini-ITX is a dummy.
Running the processor with Turbo off is a huge loss of performance, especially in a CPU limited game such as FS2020.
You can probably undervolt the chip a tad, but you'd need to run an override voltage. Trying to undervolt based off the VID without touching AC/DC Loadline causes a lot of funky **** to happen.