Once images are calculated by Autograph, they are stored in a folder defined by the General Cache section. It’s guaranteed that when you play an animation, the display frame rate in the viewer will be identical to the frame rate defined by the composition thanks to the cache which Autograph reads and displays on the fly. The cache can be stored in RAM but also on the disk; so it must be as light as possible, to avoid a bottleneck.
Most screens works in 8bpc. The Cache Previews After Quantization option is active by default, which indicates that the images contained in the cache will be stored with this bit depth. If you have a screen running on 12bpc or more, unchecking this option will produce a 32bpc cache. This is much heavier to read and therefore requires a more responsive device, especially in terms of storage, and it can offer higher accuracy in this type of colorimetric configuration.
Note that this cache is not reused by the render manager, which will produce all of its calculations in 32bpc regardless. Maximum quality will be preserved during the whole process, until final encoding in the bit depth defined by the format and the chosen codec.
Keeping this option enabled will not affect the final quality of your renders. Only the viewer will be affected and in most cases the user will not see any difference if their screen is not specifically designed for high-end color grading tasks. Keeping this option enabled also provides much better performance when reading the cache.