I am awash in paint jargon.  When I go to the POR15 site I see something called "high build primer". formerly "tie build primer"   Is it just marketing lingo or is there some implication that the primer is indeed "high" and can be sanded a bit to smooth out imperfections?  or maybe you get "high" when you use it?

As a general rule you have DTM "Direct to metal primer" not meant to go over other paint or fillers as substrates

Epoxy primers are use many times as a DTM type product. Epoxy is tough and sticks great to most anything. It does not sand very well

High build primers are primers that have thicker film build. Which helps deal with minor imperfections and sanding scratches

There are also primers that are basically liquid bondo, you see these used on show cars sometimes to allow perfect blocking and really exact edges. Evercoat makes one

Sealers are last and are used to seal down the substrate to prevent bleed through mainly. I don't run a sealer coat to date

There are tons of products available and most paint lines have multiple ways to get from metal to shiny paint. that is where I rely on the counter guys to steer me to the right products. I don't normally scrimp on material cost because better materials are easier to work with on the whole. Better paper sand better and clogs less. Powder guide coat works really good and the can I have will last me for years. I buy mid range primers, decent base coat and mid range clear coat. I shot single stage in the engine bay and door jambs...

For more jargon you could have a look at this site, https://www.autobody101.com/forums/index.php?sid=f044bf1f351a02abe241234902095df9