Your friends list makes a big difference... for example I had 100+ friends and I had about 100-120 FPs but I removed it so I only had my 5 close friends and now I play at 144 fps
there’s an odd chance that you have different servers selected on each account. may have something to do with it, but i’m not expert. getsys brings up a good point
Did you fix the issue? I've got the same problem. 90-130 fps on my main and it drops to 70 very often meanwhile on my newest alt I got 150-200 and it rarely drop. I don't think friend list is an issue as I only have around 10-20 on both accounts
Make sure all graphic settings are the same, if you have blood, bullet tracers or dead bodys On or Off could be taking affect, also could be what agents you’re playing