Preconditioning will vary based on map routing/distance/speed and battery temp. (Too high or too low). Many factors dictate when it’ll kick in or if it’s required at all.
ref supercharger speeds on shared stalls. It’s definitely been like that for most part of 2019, so wouldn’t say it’s a new thing. Rate will be cut when another car turns up on your pairing. You’ll still get the higher speed, but it’s certainly not the headline available speed for your SoC. This is not a factor on V3 charger location(s).
This has been discussed a few times on the main UK supercharger thread and a few others with graphs to back up.