HMS Vanguard 74 1787 was one of the HMS Edgar 1779 class
which was a modified design of the Arrogant 1761 class
which was a modified design of the Bellona 1760 class
I have seen nothing specific about what exactly were the modifications and if they would be significant enough to make a difference.
that the differences are not described shifts the balance to being able to use any member of any of the three classes. RMG has names for all three classes with the plans that a search brings up. The best looking plan is ZAZ0890.
Even if there was a difference for kits the compromises inherent in kit design would produce much greater difference from authentic even if there were separate plans for each class
"expert" level of workmanship.
If authentic as practical as well as expert workmanship is your objective, this pretty much excludes starting from a kit. With those requirements you should consider a kit to be GIGO.
Continuing to commission a scratch build would probably produce what you wish. By being willing to start from a kit, you are obviously not interested in a POF model. A scratch lift model with swimming body dimensions being at a painted or thin paper plates (old copper patina) would be a much quicker build. The rest is pretty much the same, except that scratch is more likely going to be to spec than what any kit supplies.
A POB two layer planking would probably get you an external layer of over scale copper or a copper foil. Both would probably be kitschy or cartoon new penny bright and very likely sporting unsightly pox-like blisters.
A 74 is a major undertaking and potentially a time sink. I have no idea about how long it would take. But if it took 1000 hours the labor alone should be $25,000.
Any less and you are expecting it to be done by a slave.