You don't seal polish.
Polish is a term used for abrasive compounds which remove (or help to remove) microscopic screatches within the paint surface.
When you have finished polishing, you wax to provide a durable layer of protection to help prevent dirt from sticking to the surface, making future cleaning easier, and help prevent things like industrial fallout, road tar etc, from bonding with the paint directly (it tends to sit on the layers of wax).
Waxes and sealants are LSPs. Last step products.
You can apply both but you would always apply a sealant first if you are using both. This is because sealants differ in their chemical composition and often prefer to bond with bare band. Where as a wax which is generally quite oily will be more happy to bond with an existing base of protection.
Products like Autoglym "Super Resin Polish" are not really polishes, more like pre-wax cleansers , filler polishes or "glazes". They are abrasive yes but not enough to really remove many scratches or swirls from your car. You might get a 10-15% correction using a product like that however the fillers and oils within the product will give the appearance of a 60-70% correction.
You need to seal or wax after these glazes or "filler polishes" because in their very nature the minute fillers and oils would otherwise wash away in a matter of weeks if left unprotected.
Locking the fillers against the paint surface means the fillers don't fade so easily and the effect of a more shiny car is maintained.
