There are two elements in charging an electric car:
1. The speed at which the charging port can push out electricity
and.
2. The speed at which the vehicle can accept a charge.
The ix1 as standard comes with an 11kW charger, so this is the fastest it can accept an AC charge, as home charging ports are 7.4kW it will draw a maximum of 7.4kW per hour irrespective if you have the standard 11kW charger or the upgraded 22Kw charged fitted.
When charging on AC public chargers, the type you get at Supermarkets etc, should the charger be rated high enough then you can draw up to 11kW per hour with the standard onboard charger or up to 22kW per hour with the upgraded onboard charger. But, this will depend if the Charging station is able to push out electricity at a faster rate, many are only 7.4kW. You can check on zapp map to see what is available locally.
Rapid charging is DC, the type you get at Motorway service stations etc, some are up to 150kW, enabling you to charge the iX1 very quickly, but the maximum DC the iX1 can draw is limited by the car itself at 130kW per hour.
Hope this helps.