2013 MacPro kept a 10.14.6 partition/whatever it is called in APFS SSD parlance and installed 10.15. Geekbench 5 says I got a 6.8% single core speed increase and a 1.4% multicore increase on the CPU test. Compute OpenCL test showed +1%.
Any of the results +-3% are margin of error in that Geekbench app. We have seen margin of error even high in some cases. No idea why that app is always so inconsistent.