Pre-render composition in file? (Adobe After Effects)
If you want instant access to a baked version of a comp, it has to be stored somewhere - either in memory or on disk. The former will limit your computing performance (eventually), and the latter needs storage space.

The third way is to duplicate the comp, including all precomps and bring in the duplicated comp as a base layer to the original comp. Since the duplicate won't refer to the original layers, it'll serve as a reference. A script to do this is True Comp Duplicator.