A stage 1+ is simply an advanced stage 1 tune, still without making any mechanical modification on the vehicle.
To be able to go to stage 1+, we will need you to provide us with logs to be able to work on each parameter individually. This makes it possible to push the preparation to the maximum while complying with the manufacturer's limits, in a purely electronic way.
If you do not have a dyno or tools to make a log, it is better to stick to a classic stage 1.