Hi
I don`t think you can make it to work whit a bare GPU in Mineral oil. You need a very good mixer and flow form the pump in front of the GPU chip and HBM also the VRM`s need`s cooling. It`s easier to just let the radiator attached to the GPU. You can remove the fans and save energy whit or without the radiator there is no gain or lose of electricity just space. But from the picture posted you have spare so put the radiator and you are good to go.
I`m doing my immersion setup right now and it`s working very good. I`m not so happy whit the result but will upgrade my pump and see how it is for now I have 13 RX 570 immersed and the power from the wall is 1500W for 31Mh/s per GPU under Linux I thing that under windows they will do better will see .