A wax when applied over a sealant will add depth to the finish.
It can also get confusing when people are talking about polishes, waxes etc. Just a brief description
Polish; is use to shine the paint surface but does not give any protection
Wax; most auto waxs have a carnauba wax base. Carnauba wax comes from a palm tree in Brazil. A good quality wax will last 3-4 months.
Sealant: is an artificial wax that will last 4-5 months.
In general terms a sealant gives a wet look and a wax adds depth so it depends on what look you are after.
I tend to go over the top and do 3 layers of sealant with 2 layers of wax over the top.
You can put a wax over a sealant but don't put a sealant over a wax.