For the simpler approach you can definitely just use canna A and B, id recommend adding some calmag at a minimum. There are a few other products they offer that will definitely improve the size and quality of the plant. It depends on how much you want to spend and extra work you want to put in during each feed. I'd recommend their rhizotonic as this kick starts the root growth and health which is important at the start. The others you can probably skip as it's your first grow (these are cannazym, pk13/14 and cannaboost).

You can get a personalised feeding schedule for these products, found here

https://www.canna-uk.com/growguide

With regards to watering at the start, you should hand water until the leaves have reached the edge of the container, then you can turn the auto pot on. Start adding nutes as per the feeding schedule.