Many Steam Linux games right now are only 32-bit, but Vulkan looks like it will be ushering in more 64-bit games. I haven't seen anything preventing Vulkan from 32-bit x86 and the NVIDIA Linux Vulkan driver is still offered in 32-bit and 64-bit flavors. With Vulkan mandating newer GPUs, game developers can at least make better assumptions that the gamer is running a modern 64-bit Intel/AMD GPU.
Croteam in their Vulkan port of Talos Principle is only exposing the renderer option via their 64-bit build. Their explanation with this Q&A is, "64-bit is the future. And present!"
I've had access to the private beta of Talos Principle for the past few days where the Vulkan code has been landing first prior to being made available through the public beta. As I reported this morning via Twitter, the Intel Vulkan driver is running into problems with the loading screen when switching over to Vulkan. The NVIDIA Linux driver meanwhile is showing a black screen with the NVIDIA 355 driver when switching the game over to Vulkan.
While waiting for the latest round of Vulkan fixes, I decided to at least do a 32-bit vs. 64-bit Talos Principle comparison with the OpenGL renderer, since this is the first time the game is shipping a 64-bit build. The initial results are good that the 64-bit version of the game is delivering a nice performance boost. The visual/graphics settings were maintained during testing.
With these 32-bit vs. 64-bit tests I did today with the Talos Principle IHV beta, the 64-bit performance was noticeably better for the high-end GTX 780 Ti, GTX 980, and GTX TITAN X graphics cards. The GTX 960 performance appeared unchanged between the two builds. Of course, outside of games, x86_64 usually wins in our 32-bit vs. 64-bit Linux benchmarks. Let's hope in 2016 we see more Linux games become 64-bit-only or at least offer a 64-bit build by default where applicable.