That's the best set-up for sure, I own a Fractal Meshify C too, white, I love it but don't think the front allows that much of intake since it has an strong anti-dust filter yet with the right fans you'll still get a-lot of air inside at least I am cooling the Kraken x3 120mm fans radiator from the outside as trying to intake but I'm sure air won't pass through the radiator that much either, so you must play with the highest static pressure fans or maybe the ones that move more air as the AF, so still anything should work in that set-up since it's the most common and recommended as top at least must always be exhaust and lower sending up is just great I want that too but this Meshify might not have such option for a lower fan, the rear exhaust is good too, it should give you no problems but I recommend any AIO for that Ryzen 9 (Pretty beautiful acquisition btw) I don't know how much they heat, my Ryzen 3 stays on 40-55 common and I have my Kraken AIO on the GPU because I do believe GPU needs more cooling than anything else just as the stock fans that come with most video cards are usually really, but really noisy and you need them at 70% to keep the GPU at 65-70 under load and that's a no for me, I set up the card vertical and had to literally destroy the back panel to open for vertical card, it was no much of an issue and I don't regret it now the case looks awesome ^^.
I would like to know how much room temperature affects the chips in themselves since you know most likely room temperature will only change the intake of air and still the chipsets are quite seal by the coolers usually so I believe the room temperature should do some change but it shouldn't be too much.
GPU today woke up at 32 degrees, almost my record and keeps on 35-37 idle after some time up then it doesn't pass the 45 degrees on full load OC.