Reports that are aimbot related cannot be handled instantly unless the said user is being totally blatant with it. You will definitely need to record to provide admins with the evidence if you want to report someone for aimbot, because we can't judge whether someone is using an aimbot or not by kill list or your action logs. Also, it's not smart to mention names of people you think are aimbotting, because that will just make them more cautious and will make our job of detecting aimbotters even more harder.
Tldr: recording is a must if you want to report someone for aimbot. For nvidia use shadowplay, for amd use relive and if neither, use OBS