If you want an mATX but have no compromise in terms of silence and cooling there are VERY limited options.
However, those options that do exist are kinda great.
If you can find a proper mATX or ITX MBO, and you want a silent and cooled high-end PC, then this is the way to go:
Define Mini C with three Silent Wings 3 PWM fans - 1 120mm back, 2 140mm front. These fans are inaudible at highest speed and offer great CFM at the same time.
If you can't find a proper mATX or ITX MBO, then you can go with ATX but still have a small case. It's the Corsair 400Q, it is almost the same dimensions as Define Mini C, just slightly taller - only 5cm difference in height. It has everything else identically to Define Mini C: PSU cover, fan setup, noise isolation. So, the same fan setup as before. There really is no other such borderline SFF mid-case with those feature.
However, those options that do exist are kinda great.
If you can find a proper mATX or ITX MBO, and you want a silent and cooled high-end PC, then this is the way to go:
Define Mini C with three Silent Wings 3 PWM fans - 1 120mm back, 2 140mm front. These fans are inaudible at highest speed and offer great CFM at the same time.
If you can't find a proper mATX or ITX MBO, then you can go with ATX but still have a small case. It's the Corsair 400Q, it is almost the same dimensions as Define Mini C, just slightly taller - only 5cm difference in height. It has everything else identically to Define Mini C: PSU cover, fan setup, noise isolation. So, the same fan setup as before. There really is no other such borderline SFF mid-case with those feature.