Keep in mind that I have a 300g mixed reef system (DT + sump), and a skimmer, UV light, ATO, automated water change, RODI+ water mixing setup, flow meters, dosers, and a calcium reactor. That may be way more than you will ever need in a 20g tank!
The Apex is involved in almost all of the mechanical processes in the tank. It monitors my return pump flow so I know when it is becoming obstructed, it manages the pH and flow rate through the calcium reactor, it controls the top off pump, runs the auto water change, makes new RO water when I need it, turns my skimmer on and off based on when I feed the tank, controls my heaters, runs my dosers, and I am sure I am forgetting something.
I travel a lot, and the remote monitoring gives me peace of mind in case my family isn't able to watch the tank. I was half a world away one time when the Apex notified me that the UV pump had failed. I was able to remotely turn the UV light off so it wasn't going to overheat. I lose power alot, and the Apex lets me know when that happens. My son called me one time to let me know that the skimmer was overflowing, and I was able to shut it down remotely. When my water level drops or increases unexpectedly, I am notified and I can try to take corrective action remotely.
All those things aren't "must haves", but they do make things easier for me. In your case, I don't know what tasks you manage today for your tank so it is hard to say how it might help you other than the sure thing of being able to at least monitor some things - even if only temps and pH - while you are away. The next thing most people do at some point is set up an ATO, if they have the room. After that, it gets to dosing, water changes, stuff like that.
I will say this - I have 6 other small tanks that are all fish-only, and I don't have the Apex doing anything with those ...