Your boyfriend and I would probably get along. I too like playing games 'efficiently' (I've heard folks refer to this as 'min-maxing') and I've spent the entirety of my time in Dreamlight Valley thus far amassing several million gold, all the while my house and village look like it was hit by Katrina repeatedly. And since that's how I play this game, I would actually be really appreciative if someone were to do the things you described your boyfriend doing. Obviously that's not how you like to play these kinds of games and you're totally justified in your frustration.

So I guess the reason I share this with you is because I wanted you to consider the possibility that he is doing this primarily out of ignorance rather than disrespect. From his point of view, he might think he's doing something really nice for you! So instead of "calling him out" on it, take this as an opportunity to educate him about your likes and dislikes and ultimately, how you would like to be cared for. If you're worried about him 'throwing a fit', I'm going to assume that like me (and a lot of men in general), he's got some insecurities so here are some things you can try to help make that conversation easier:

1. When you talk to him, it might help to start off by letting him know how much you appreciate the thought behind his gesture (even if what you're presently feeling is far from 'appreciative'). "Hey [name], thanks for helping out around my Disney village. I feel like you put a lot of time and work into it and I'm grateful that you're willing to share in my interests and eager to help!"
2. Keep it light. Personally, the more serious the conversation, the more I feel like I've somehow failed as a boyfriend/significant other and that's when I'm most likely to say or do something dumb. So it can be helpful to stress that this isn't really a big deal: you like to play one way, he likes to play another, no biggie. One thing my wife does that's really helpful at de-escalating/defusing situations is saying tough things with humor so maybe crack a joke or something if you feel comfortable doing so. "But you should know that it made me a little sad to see that all my clay was gone... Clay is just very important to me. Clay is life. I am the clay queen. But with no clay." (I dunno, sorry if this is cringey, just trying to come up with an example).
3. Give him a specific job or a challenge to tackle. It's a way to show him that even if you don't personally share his style of gameplay, you acknowledge and value his way of doing things. "I personally don't like playing games super industriously but I am kinda curious to see what a super industrialized village might look like. If you're into that, you should create a village in that style and we can compare our villages!"

In any case, good luck and god speed!