Don't be afraid of Iso, you might want manual focus, mirrorless cameras even as good as the R5 have a hard time focusing on "nothing at infinity". Largest aperture your lens can do (biggest hole, smallest f number) and the recommended shutter speeds.

I had luck with iso 3200, f1.4 and 1/6s shutter handheld on a sony a7iv with a 35mm f1.4 GM.