See, I think that a first is too high - the opportunity cost becomes too great because you are essentially buying two years of top flight DE (presuming a cut date of 6/2/2027 to get the most out of him, maximize early savings to invest in new talent, and maximally delay the 10M dead cap) for a first rounder.
Send a second round pick, and you are trading four years of a controlled-cost rookie for two years of top-flight veteran. Send a first round pick, and now trading a potential of five years of controlled cost, which goes to a prospect that one assumes is more likely to get that next contract with your team. It is better to draft a DE in the first, in my view, than to trade a first round pick for a DE, because that player gives you a competitive window of 2026-2028 before the fifth year option is exercised. That aligns with the team interests because those are years where Williams has more experience and is more competitive than in 2025, which is likely to be Garrett's best year for the team (assuming that he experiences a decline with age).
Hell, if you send Chicago's second for him, you can still draft a DE in the first round. Garrett's contract doesn't lock the team out of looking for OL in FA, and drafting more OL with the CAR second and CHI third round picks. At the core, what I want to stress is that Garrett's current deal is not too expensive for the team. That would give our defense a competitive window that matches the early years of Williams when he is on a rookie contract, and stays competitive for the first year that Williams is expensive.