Bear in mind that the iPad Pro A12X benchmarks put it on a par with the 2018 i7 15" MacBook Pro.
Now, I'm healthily sceptical about the chances of it beating an actual i7 15" MBP in real life, but I'd say that was more than good enough for a MacBook Air/12" MacBook type of machine, which is going to be where the ARM has the initial advantage.
It would depend on the workload I guess but I have tested around with actual real world calculations in Python between the iPad Pro 2018 and the i7-9850H in my Lenovo and the latter is only 15-20% ahead. So against the 8750H in the 2018 MBP it could be decently close depending on workload.