Evil Hurney

Spotrac has his value at $14.7M a year (https://www.spotrac.com/nfl/carolina-panthers/taylor-moton-21806/market-value/) OTC estimates the franchise tag for an OL is about the same money (https://overthecap.com/franchise-transition-and-rfa-tenders/). Seems reasonable as a starting point.

Assuming the team is trying to win and not tank then option A for me. A backup QB in general isn't that expensive in comparison to a starter ($8M gets you in the top 3) QBs can be a good currency, almost as good as draft picks (see Eagles)

Not a chance. Once the JETs get another QB (Watson or QB at 2), Darnold's value plummets to a 2nd rounder at best -> see Josh Rosen.

Considering it will probably take 2 firsts to snag a non-Lawrence rookie QB of your choice. 3 firsts for a young and proven Watson seems like a MUCH better deal.

A slightly different view...The teams picking after 18 are playoff teams meaning it should be harder for a rookie to come in and contribute day 1. Also, trading down in the early rounds to get additional mid round picks (based on current draft pick values) is generally a good thing from an approximate (player) value standpoint (http://www.footballperspective.com/creating-a-draft-value-chart-part-ii/).