The E cores on the original M1 and M1 Pro chips appear to be managed quite differently, with respect to the performance of background processes at low QoS.
AsmAttic
Obtaining estimates for individual P and E core performance of processes run mainly in an ALU and those using floating-point and SIMD gives further insight and confirms the cores haven’t changed from M1 to M1 Pro.
How does macOS load processes onto the cores in M1 series processors? Are its policies similar between the original M1 and the M1 Pro?
Geekbench 5 scores for the M1 Pro are around 2800 single- and 12500 multi-core. Do they represent maximum performance, though?
Explore running test code of different types on the different cores in your M1 Mac. Provides insight into how your Mac performs, rather than just how fast it is.
The Eclectic Light Company 