> giving you more data resilience in short term but wasting more write cycles because they're technically writing 1111111 instead of 1. every time.
No, that's not how it works. SLC caches are used primarily for performance reasons, and they're faster precisely because they aren't doing the equivalent of writing four ones (and especially not seven!?) to a QLC cell.
so if under provisioned now they work as pSLC, giving you more data resilience in short term but wasting more write cycles because they're technically writing 1111111 instead of 1. every time. if you fill them up then they have less data resilience.
and the best part, there's no way you can control any of it based on your needs.