The French subjects have their own gameplay and actions, related to their relationship with the French sovereign, and if they stay loyal to them, or not:

So, at the end of the day, one of the contenders will probably be strong enough to defeat the other. In the case of France, it’s straightforward: No more independent English presence in the continent. In the case of England, beside pure conquest, the ‘Claim of Throne of France’ peace goal requests:

England (or their subjects) must control more than 15% of the ownable locations in the French Region
England must control the capital of France

The cost of this treaty also depends on 2 factors:

A base cost
A fluctuating cost based entirely on the relative strength between the two countries. So, a stronger England would inevitably make this peace treaty option somewhat cheaper.