About joseki and using pro game databases: unless you are aware why a joseki is good and why pro players play certain move, you’re not going to be able to take advantage of your opponent when they stray apart from conventional moves.
Actually, many joseki are not even the optimal play, as we have seen since AlphaGo taught us improvements of century-old patterns. It is likely that current day AI also makes mistakes, and that there exist even better joseki out there.
And, how good a joseki is, will strongly depend on the overall position of the game. Some joseki are considered good, but also very difficult to use.
Finally, as others have said, joseki and pro game databases will only get you about 20 moves into a game that lasts 300. I’d say that most points actually get distributed in the midgame, rather than the opening. There are even people who can gain a significant advantage from being good at just endgame.
The only real mathematical approach to go strategy that I’m aware of is endgame analysis (and only the very last part of endgame). The opening, midgame and early endgame are all done more intuitively than mathematically (not that those two have to exclude each other, on the contrary, mathematics done well should be intuitive).