J.J. McCarthy performed well in his first start for the Giants, showing promise
That said, both sources carry only 50% confidence, so you should hedge hard on how much stock to put in "showing promise" in a single start. Don't bench or start anyone based on this yet in redraft leagues — McCarthy shouldn't be in your starting lineup conversation this week given the uncertainty around his role, snap share, and whether this start is even repeatable with a new team and presumably a compressed learning curve on the Giants' playbook. If you're in a deep dynasty or speculative add league, this is worth a low-cost add to stash and monitor, especially if Daniel Jones or whoever was ahead of him is banged up or struggling — a quarterback change with early positive reports is exactly the kind of thing that can snowball into real opportunity.
Bottom line: track McCarthy's next start before committing any real FAAB or trade value. The storyline is interesting and worth a speculative roster hold, but with impact scored negative and confidence only at 50%, this is not yet actionable for your starting lineup. Revisit after a second data point confirms whether the "promise" extends beyond one game.
Cast off in Minnesota, McCarthy is trying to resurrect his career in New York while also leading the Giants to a division title.