When upgrading a card, is the subtitle used to determine the difference between cards when the title is the same (I'm referring to any of the "unidentified/unknown" cards that take a couple packs for the real use of the cards to be known)? So if I chose both versions of strange solution (acidic ichor) would I have to spend another 4 points to change one of those versions into strange solution (restorative concoction? Or, because it's the same titled card, would I spend the difference to a minimum of one point?
All higher-level versions of these cards state they must be upgraded from the lower-level version. So you cannot change Strange Solution (Acidic Ichor) into Strange Solution (Restorative Concoction) at all.
You can only include this asset in your deck by upgrading it from Strange Solution (Unidentified), and only if you have "identified the solution" in your Campaign Log.