I regret I will put a ‘spade’ into the previous comments and suggest that if the weight of the van will not be adversely affected significantly, then an A/C can be a blessing. While if you tend to stay in the middle of France for your holidays then a fan will be sufficient I can only state from a lot of experience that in the ‘deep south’ it is the difference between a good night’s sleep and a lot of tossing and turning.
When the daytime temperature hits 35 plus degrees then the temperature at night will not drop below 30 until the wee small hours. Your van has also heated up and takes a long time to cool down. When you put your hands on the inside roof panel, and it is very warm, then you know the van is ‘cooking’.
A fan will merely blow the hot air around, it will feel a bit cooler, but is not really doing anything. As for the noise, this depends on the unit and installation. We have been next door to units with both roof mounted and internal A/C units and the noise was no more than a buzzing sound, and unless your open window was next to it, not really a problem. Also most campers are tolerant and switch the A/C off after going to bed with an ice cool van to relax in. I fully admit to being quite envious, after a good few hot sticky nights, and have seriously looked at the possibility of fitting an internal unit to my van, but the loss of 20 kg of payload is a big factor. Many modern units are designed to not overload and average camp EHU, so my advice is look at where you wish to spend most of your time and if your wallet and weight will allow it, then go for it.