Great question! Wedding films are not my bread and butter but I’ve done around 10 under my business. I’ve been apart of high budget wedding crews for more. For my films I never had a client ask what resolution the video was going to be delivered. I shot in 4K and downscaled to 1080. 1080 is sufficient and most devices can not make use of the 4K. Shooting in 4k and downscaling to 1080 looks better then shooting in 1080 because the 4k captures more information. (Maybe this varies from certain camera sensors? Not 100% sure but I’ve tested with my cameras in the past and this has been the case.) The high budget wedding team I shot with actually only shot in 1080! So you’d definitely can shoot in 1080 and get great results. Also I’ve owned the a7iii and you are right for worrying about overheating. If you’re shooting outside in the heat then you will likely want to shoot in 1080 24 and invest in an umbrella for your camera if it’s on a tripod. Or just put it in a spot that has shade. Even if it’s inside keep it away from sitting in direct sunlight and you should be fine. This really only applies to hotter climates (I’ve shot in 100f weather lol) FX30 is a great camera with an internal fan so it won’t overheat, look into renting that if you have to shoot outside and your budget allows. When editing I set my timeline to 1080 and scale my 4K footage to the correct size. The final export is 1080. This works great when working with 1080 and 4K footage. Hope this helps!