My old DJI RS 3 mini is still a good gimbal for EOS 5D Mark IV.
EOS R1 or EOS R3.
Get the Sigma 56mm f/1.4 DC DN for RF mount.
Also recommend the Godox V1.
EOS R10 supports UHS-II SD cards, so the best choice is to get a UHS-II V60 or V90 card, I got Lexar 128GB Professional 2000x V90 card, very fast.