I was curious myself regarding Optiseal so i checked on the optimum forums' FAQ section:
Dose Opti-seal lock in my Carnauba?
"No. The solvents will dissolves carnauba floating it to the top of the
Opti-Seal. This fact holds true with any solvent based WOWA sealant.
The carnauba is not removed just repositioned.
Both methods in theory should give the same results. If it were me I would apply the Carnauba first.
Doing this will help the foam applicator pad glide across the paint much easier."