When I went away for 10 days in summer 2018 I was worried about various scenarios which could have happened. For the weeks leading up to the holiday I did dummy runs, ie, different feeding options, didn't top up evaporated water levels, no vacuuming etc etc. I just kept a beady eye on what was going on and towards the end of the 10 day dummy runs i'd test the water to give me an idea of nitrate build up.
By the time the actual holiday came and I was away for real I knew what I needed to do.
1. Big water change the night before going. When refilling after said water change I put enough water in the system, more than usual, to cope with evaporation.
2. My neighbour came and fed the fish, every other day, and the very bare minimum at that.
I knew that when I got back that my nitrate would be around a certain level, and it was, and I knew that the water level in my sump would be at a certain level, and it was.
That holiday has left me with complete confidence now for any future holidays I may have. You just need to put the work in beforehand.