We'll have to see what they actually come up with. They were oddly quiet on the performance implications of the switch yesterday, they did show them doing video work on the new Macs but they're clearly not ready to say the benchmarks.
That said the iPad Pro, last year's one, does really well at video encoding out performing Intel Chips:
https://www.tomsguide.com/us/new-ipa...ews-28453.html
I am not sure how Apple gets around that performance issue but they are heavily adapting the ARM architecture and they use other chipsets. I think on the modern Macbook Pros they throw over some tasks to their T2 security chip.
If they can do that with the iPad then in theory they should be able to push it even further with the extra heat capacity they'll have in a larger Mac.