Question How can I, in an easy way, make sure that all presets have the same output level

There is no "easy and fast" way such as adjusting a single parameter for all presets at once; you'll need to adjust individually the output level of each of your preset. This is done in the LEVELS menu: use parameter LEFT output (and RIGHT as well if in Stereo). The parameter has a small "p" in the right side of the display meaning that the setting is at preset level.