eGPU Mac Mini, dual monitor, performance

Been working for about a year with a 2018 Mac Mini (3.2 GHz 6-Core i7, 64GB) with Radeon Pro W5700 eGPU w 8GB RAM), using an Eizo CS2740 display (3840x2160). My wife "donated" her LG 4K to give me more screen space, but I'm wondering if it's slowing my system down. The LG is TB-only, so I can't plug it into the eGPU and it's connected directly to the Mini with it's underpowered GPU. Question: Am I slowing the system down with the LG plugged in to the Mini? I've noticed render times in FCPX seem to take a bit of time lately. Any feedback appreciated.

I can confirm same with Macbook pro 16 with eGPU (Vega64). When I connect external monitor directly to eGPU, fcpx works smoother, rendering, export is quicker. When I use thunderbolt->displayport cable and connect Dell monitor to Macbook, fcpx especialy at timeline dont use egpu at all. Only exports and not with full egpu power. This happened at previous fcpx version 10.4.9 and 10.4.10 didnt fix it. And there is one other terrible bug from version 10.4.9. If you use eGPU with monitor connected directly to eGPU, InertiaCam stabilisation will not work. Smoothcam work without problems. If I connect monitor to macbook directly or turn off egpu, InertiaCam stabilisation start working great. I reported it to apple 3 weeks ago. Hope they will fix it.