Pre mixed bases with VG/PG ratios already set would just confuse the hell out of me personally. I like simple, to be sure. That's why my mixes contain only the PG that is already in the flavors and the nicotine and once these are in the bottle I'm gonna use, in with the VG till full. Cant get any more simple than that. And if this seems a little thick mix, add a bit of PG if needed. I gave up trying to get exact PG to VG ratios long time ago. It's not even that important really. If you're mixing for pod use or some MTL
devices, shoot for a bit less VG so that the pod will wick sufficiently. Flavoring percentages are more important in my mind than how much your base ratios are. But that's just me.