If they integrate Steamworks, these games usually (not
always, but exceptions are rare) will not start up if Steam isn't running. I am speaking as someone who cares about and tests this.
Ironically, I have actually had far more success with stuff from the Epic Games Store. Lots of major titles such as Beyond Two Souls and Ratchet & Clank: Rift Apart function as completely standalone, DRM-Free binaries once downloaded, it's great.
