It is good to use the estimated wattage and increase it by 30%, that is useful to be safe, so 750 should be ok, BUT the thing is, amd official recommendation, says it is better to use 850 watts for that gpu. Here the link
The seasonic PSU that I recommended in one of the builds, I think it would be good for you, as long as you do not mind that it is not modular, if what you want is a modular psu, in one of the builds, I think there is a corsair 850w gold certified.
The case, if you are looking for a white one, as a personal opinion, I think the one I recommended in one of the builds is a good fit (Fractal Design Pop Mini Air MicroATX), it seems to have good airflow, white and the video card should fit with room to spare by 25 mm.
Yeah, in my opinion I don’t value so much if the psu is modular or not, I’m more of a functionality over look/ease of use kind of guy, but if it’s your first build, yes it might be good to go for a fully modular one.
I did a quick search and found 3 that might be useful for you and stay close to budget (850w and gold certified): -SeaSonic FOCUS GX full modular 135 euros. -Corsair RM850e (2023) fully modular 130 euros. -SeaSonic FOCUS semi modular 110 euros
I think that with any of these 3, you would not be making a mistake.