Just an an update I went to the same sim using the same draw settings....
On iMac M3 with 24GB RAM the fps varied between 42 and 36 FPS
On MSI Laptop with RTX4070 the fps varied between 170 and 140 FPS
These were not deserted sims but an event sim from the destination guide with people popping in and out all the time but on average 15 people on sim and within cam range.
The iMac can cope with it but it's not as great as a machine which does not need to convert the code from a different processor and has dedicated gfx.