I'm probably one of the first group of buyers for this, and I see there are some missed in the review, and not just here but elsewhere too. And I start getting question on reddit about this. So I figure I posted here also.
There are two major poorly design choices about this case. And let's started w/ what every reviews I have seen missed.
1. While B660 have two 2280 NVMe slots, the one on the back is not ideal place to use card w/ double sided chip nor card that require heatsink. Generally speaking gen 3 card do not need heatsink. And gen 4 generally do. I stated this because the NVMe slot on the back of the board is not raise very high off the board and there are some circuitry underneath. I think you can imagine what would happen when you attach heatsink around (including metal plate on the bottom of) the NVMe stick and touch the pin spike off the back of the board.
2. I think B660 is not well design in term of heat dissipation. W/o GPU it's fine; but w/ GPU it suddenly become a heat trap. It's practically not cooling off myself, and some mods are required to cool the darn thing off. The biggest heat spot is actually right around the CPU area. The problem with the case is there is practically zero exhaust air flow. If you look at the pictures (horizontal orientation w/ M/B laid out on the bottom), you have the bottom w/ zero air flow due to M/B). One side of the case which could put the rubber feet on is solid, meaning no air flow. The opposite side of that, if GPU is install, it's then become intake fan and the GPU block off the air flow. Right above the CPU is the PSU. So, technically the only two areas that could provide good air flow are, front and back. The back are largely block by PSU. But the biggest mistake ASRock did was the front. If this case is designed so that it's slightly deeper and the metal plate to mount the extra SATA drive is more perpetrated and the plastic front is meshed then it could mount 120mm fan there and this would fixed a lot of problem.
There are some mods that can be done w/o physically damage the case. 1. mount a few 30-40mm fans underneath the PSU as exhaust. 2. mount some fans directly above GPU (inside the case if space is still available) or outside as exhaust but route the fan cable on the back above the GPU mounting plate. The flip plate is removable, and you will just have to screw the GPU down instead of using the plate to lock down GPU.
On the other hand, w/o the care of damaging the case, user could cut or drill some holes on the front of the case and mount the 120mm fan, and that maybe the best way to cool the unit. But I would put extreme caution on doing this. Make sure you have the M/B out of the case first. And clean the case w/ extra caution after cutting or drilling hole on the metal plate. Files and sand the holes well after. Any small piece of loose metal shard flowing inside the cause could turn your PC into door stop or even even your house into ash.
I would consider the first point as maybe negligent or not thoroughly thought design choice. But I would consider the second point as poorly design choice. I mean the case is definitely designed w/ low to mid-low tier GPU in mind, otherwise why even put 500w PSU in there, but w/o even consider adequate cooling at all.