Not all sealants or flag are the same. A properly designed pool having a salt cell should not have any additional problems that aren't also considerations for those with erosion (tablet fed) feeders.

More important is the sealant and flagstone used.

Scott

What type of sealant is recommended or best to use.

Check with the local stone dealers or masonry suppliers. They normally have a selection they know something about while HDP or Lowes won't have anyone that can really help.

There are flat finishes and glossy finishes available. It depends on the look you want.

The better sealants are not cheap and will vary by geography.

Scott

Sorry, I disagree poolguynj (Hi Scott!) about not needing to seal the stone for a salt water pool. You might get lucky and never have an issue, but you would probably be in the minority over time. Perhaps it is a geographic thing. I am in Texas where it is a big issue. The good stuff is very expensive like DuPont StoneTec Professional Sealant for Salt Water pools or DecoShield Plus Stone Sealant. These will last longer. The stuff you get from your local hardware store needs to be reapplied at least annually. Depending on what your PB charges to seal, you may find it makes more sense for you to apply the sealant yourself.Just be sure to power wash all the stone and let it dry before applying the sealant.