Jordan
From the 2 ATO systems you posted - I am not a fan of the Autoaqua because there appears to be no 2nd failsafe switch. The Tunze has a mechanical float switch as a failsafe. I think the 2nd failsafe is a good peace of mind investment.
I use the JBJ for my nano - its a lower cost option.
If you go with float switches controlled by the Apex - I would use 2 - one as a failsafe. The ones sold by DA are good. I saw somewhere they actually sell optical stand alone switches now. There is another vendor autotopoff.com that specializes in DIY ATO stuff. I think the hooded float switches they sell are the best out there.
You will also use one of the Apex outlets for your ATO pump. Keep in mind the small pumps like a Tom Aqualifter cannot be controlled except by one of the relay switches (outlet 4/8). This is because of the low power requirements of the pump.
You need to also program a time failsafe - the programming for this isn't intuitive - but you can re-post when you get there.
I didn't go with the Apex option because it will use up one power outlet and 2 inputs which are resources I could use to control other equipment - when I can just get a stable ATO system for about $150-200.