Ground Clearance:
XC40 P8 Recharge = 6.9 inches
Polestar 2 (Based) = 5.9 inches
Polestar 2 (Perf Pkg w/OHLINS) = 5.7 inches
Based on this, I’d anticipate you would not want to lower the car more than ~1.5 inches. Any more than that would not only risk damage to the battery pack and underside of the car, but also might over articulate the control arms. I’m guessing you wont be able to dial back out all the negative camber from the car, either. I’d be curious to see if you could retrofit the OHLINS setup from the Polestar 2 onto the XC40, though, as that might provide you the height you want.
(Note that the XC40 is 4,740 LBS and the P2 is 4,680 LBS so they are close enough to allow for this, and do share the same platform). I’ve actually been considering a P2 for myself, to match my wife’s XC40 P8. If that happens, I’ll try to get some photos of both suspension setups. But, I doubt she’d let me lower her SUV anyhow haha