Williams is due $33M in 2026 and obviously the 49ers don't think he's worth that amount. In 2026 the 49ers will be accounting for $13.3M in dead money that they had previously paid Williams but hadn't yet accounted for. That $13.3M cap hit is set in stone. There is an additional $20.83M in dead money that the 49ers have previously paid Williams but haven't yet accounted for. That future dead money is due to be accounted for in 2027.
If the 49ers release Williams with a post June 1st designation that future cap hit would remain in 2027. If they otherwise release or trade him before June 1st, (and a trade looks unfeasible), the future cap hit would accelerate into the 2026 cap calculations. This wouldn't be disastrous as the 49ers wouldn't then be accounting for $25.5M of the $33M they were due to pay him.
Ideally the 49ers would like to reduce Williams' 2026 pay to his market value and then push more of the 2026 cap hit back into 2027. How much of a pay cut Williams will accept comes down to what he thinks the market will pay him and how much, (more or less), he'd rather accept to stay in San Francisco.