40: non-performance (silver brakes)
34: performance
So either version will fit on either vehicle with OEM 235/35 “TO” PS4Ses. The difference is that the ET34 are intended to maintain the correct scrub radius for vehicles with what was originally called the Performance Upgrade Package, while the ET40 maintains the correct scrub radius for non-PUP vehicles. Scrub radius is only critical on the front axle so you could use either offset in the rear with no negative effects other that the inability to perform tire rotation maintenance (which is required for Michelin treadwear warranty).
I see people putting stupid-huge spacers and crazy positive-offset wheel packages on 3s constantly in order to get the look they want, throwing scrub radius (and handling characteristics) out the window, so you decide what you want. If you do though, know that deviating from the factory offset *will* affect driving characteristics some degree.
There is speculation that the ET34 on PUP allows slightly more scrub radius in order to optimize cornering performance over efficiency. The OEM PUP wheels are ET35 which likely results in identical scrub radius as the ET40 wheels on non-PUP 3s.
For those curious if 265/35 PS4S will fit, I’m doubtful as it would be extremely close to the front steering knuckle based on how close my 255s are. However, if you happen to have a non-PUP car, but ET34 ZeroGs (eg, you bought them from Tesla or a 3rd party), I think the extra 6mm of inside clearance would be enough to do the trick, allowing 265/35 PS4S to fit without a problem. Again, it might fit on the standard offsets, but might not. We wont know until someone tries, but at $340 non-refundable once mounted, it could be an expensive experiment. If you have a PUP vehicle but ET40 ZeroGs, I’d say chances of 265/35 PS4S fitting w/o hitting the front steering knuckle would be slim-to-none, plus your scrub radius will move from positive to negative, resulting in the need to tweak toe-in from normal for best performance/efficiency and cornering performance characteristics changed quote a bit.