BUILDING THE SYSTEM
As always the purpose of this section is not to build a functional system but rather to showcase what you can expect from the case at hand in terms of interior space.
Even by installing a full ATX board the Redline RL06 PRO has quite a bit of available space left inside.
Unfortunately although you can indeed install a 240mm radiator at the top it needs to have a maximum thickness of 30mm so that pretty much rules out every AIO system out there and most radiators (with slim fans perhaps it would be possible).
With enough room for CPU coolers up to 158mm in height you should be able to use most in the market today.
Even if you do mount a radiator at the front you should still have enough room for even the longest graphics cards.
In terms of PSU space you can mount regular ATX sized ones without issue as you can see from the above picture (anything longer and it may not be easy to route cables).