Hey y’all! I work on Apex Build and Release as the Steam engineering owner & helped ship this extra launch option this week.
Basically the DX12 client takes advantage of some modern APIs for rendering and CPU optimization. If you’ve heard of RHI (rendering hardware interface), it essentially implements use of this into the game. Generally you should experience better overall performance, especially on newer hardware like high core count CPUs or modern GPUs. If you’re streaming / recording while playing from a single PC you may also see some performance improvements.
I’ve been using the DX12 client for a few seasons on live and suggest giving it a shot!