If you store all associated files and necessary docs (for example, presets, use DNG, etc), yes, you can have one SSD with everything necessary and move it from Mac to Mac. You'll need to use the Store Presets with Catalog option for one, again, that stores those presets on the drive, not deep within the Library. Profiles are also an issue that DNG should solve as they are within the DNG, but you should test this with new, imported images. You may need to sync your profiles and such on both machines. You'll need the LR application preferences to be in sync as well. The downside is complication syncing whatever needs to be on both machines, but otherwise, it is doable.