Help Choosing a Pre-built Gaming PC Please

New PC acquired. 8700k CPU, 2070 GPU, 16 GB RAM. 1 TB SSD.

FPSs are great for most things, nearly double for Battlefield 5 over the prior computer, same settings. 3DMark went from better than 38% to better than 85%, with FPS climbing from mid 20s to mid 50s.

Yet for Total War: Warhammer 2, I get FPSs in the 30s in big battles, same as with the old computer. Bizarre.

I don’t get it. Why would this be?