So a few things.
1. if you are taking about Essence EXTREME, then yes, you can use it with reload, of course, just making sure you Eraser down the car to make sure no oils are going to prevent the reload from bonding.
2. Wax can go on top of reload. But reload, cannot go on top of wax. This is the same issue as previous. the wax creates a layer on top of your paint that prevents the bonding agents of the reload from reaching your paint. This means that the reload wont ever bond correctly and you wont be able to have it stick to the vehicle.
3. If you are talking about Essence PLUS then reload will stick on top of the product, but its recommended to wait about a day or the reload may not bond as well as it should on top of it.
Hope this helps.