I was wondering the same thing, And I according to Optimum Tech's channel on the ncase m1 here the best air cooled configuration for the case is with 2 fans on the bottom, he uses Noctua Nf-F12 fans on the bottom but in a later videa swapped them out for NF-A12 premium fans which sadly at this time only come in noctua crap brown color until chromax line comes out next year. Given that the FE 3080 appears to be slightly thinner than the 2080 Super, These fans should s till fit on the bottom. I also ordered a smaller noctua fan for the rear of the case as an exhaust to assist with the new 3080 fan design and it should fit nested behind tha AIO of your choosing.
The Arctic P12 PWM fans have been getting good reviews lately and are cheap enough that you could even get them as temporary fans until the Noctua Chromax A12 comes out.