Performance & battery · Performance modes
What is Extreme performance mode, and when should I use it?
Short answer: Extreme lets background work use more of your Mac's spare capacity so long jobs finish sooner. You choose it yourself; it still yields to your work. Best used when plugged in and away from the Mac.
Extreme — fastest, uses more lets Storage Studio's background work use a much bigger share of your Mac's spare capacity, so long jobs like building your storage profile or measuring a large drive finish sooner.
It still yields as your Mac fills up — it uses a share of what's free, not of the whole machine — and Storage Studio still eases off while you're actively typing. It's never chosen automatically; you pick it, and it stays until you choose another mode.
Good moments for it: your Mac is plugged in and you're stepping away for a while. On battery it will use more power than the other modes, so switch back to Automatic afterwards.