It means a lot of things will revert to software only modes. Some simple effects will likely continue to work with GPU acceleration but more complex ones like Lumetri won't. Likewise, Warp Stabilizer, the 3D camera tracker and a few other functions that draw overlays may no longer work. And yes, of course a lot of things will simply feel a lot slower when e.g. hardware accelerated decoding of MP4 files isn't available.