Hi Tomas,
If you upgraded to 90 kWh, the weight of your car and your kWh consumption would be exactly the same as it is now. However you would have 280 rated miles instead 265 and your supercharging speed would be much faster. The 90 kWh packs supercharge faster than the latest 85 packs. Therefore they will supercharge much faster than A packs. Unfortunately I don't have specific data about A packs. If you supercharged a non-A-Pack loaner you might have an idea about that. If you want to compare supercharge times of a non-A-pack 85 kWh to 90 kWh, there is a calculator for that here.
15 to 16 miles more rated range can be useful in a number of different ways. You could increase your speed between superchargers that are near range limits. You could have more buffer and skip a station that you couldn't skip before. To try out these kind ideas and play around with speed, there is this calculator that I mentioned two messages ago. In both calculators you can select S90 to represent the upgraded version of your car. Have a look at this image.
