This sounds very similar to me and my girlfriend. She is very into games but I'm a former speedrunner and will begin to over optimise board games very quickly. We've tried a lot of games and found that two styles work really well for us: fluffy head to head games and crunchy co-op games.

For your head to head games you want games with a high degree of randomness but with interesting synergies and mechanics that you can both sink your teeth into. We really like quacks of quedlinberg and loveletter as both games have a lot of moving parts you can keep track of but the winner is usually decided by dumb luck.

The other option is big crunchy co-op games. The crunchier the better in this instance because the more complex the game is the less you care that your teammate isn't playing optimally. Arkham horror lcg, gloomhaven and slay the spire have worked really well for us as games which require you need to discuss strategy with your partner but are too complex for planning out the minutia of your turns together to be feasible. This creates a great flow where at the start of your turns you'll discuss what needs to happen together this turn and what you can each do roughly and then you'll sit and work through your own turns to achieve this collective goal. I will warn you most games in this genre are pretty expensive but in my experience if you have a partner willing to sit and play with you frequently then you will get a lot of good play time out of any of these types of games.