For those who are wondering whether a 280 AIO / radiator might fit side-mounted: Yes, it does. Tested with the be quiet! Silent Loop 2 280 (314 x 140 x 27 mm, 1x 140 x 25 SW 3 + 1x 120 x 25 mm SW 4 HS with Noctua adapter).
Using an AIO, there is just this issue, that the in / outlet ports of...