I'm trying to purchase the above mentioned case and I'm not sure if this one supports TT Premium PCI-E 4.0 Extender 300mm with 90 degree adapter or TT Premium PCI-E 4.0 Extender 300mm.
In the document for C31(https://www.thermaltake.com/media/productattach/c/a/ca-1n2-00m1wn-00_commander_c31_tg_argb_manual_190102_o_.pdf) case it seems to be a regular one but this is not confirmed anywhere.