In the case of a network where the client's requests are universal, opting in and out of certain websites to your preference to save money shouldn't be necessary. The ISP is not spending any money providing or denying service to another website alone, and therefore should not be able to throttle your access to said website. The ISP shouldn't be able to charge you to another section of the internet because they do not own it, or spend money on providing the client with a connection to that service.
They already do this though. Pre-net neutrality you still pay for the package of all services being offered, they dont have to charge you for this package of services, its just an extra fee that they tack on to their universal plan to make more money. Post-net neutrality will still have the same exact fees that they add to packages of services, which again are completely arbitrary and unnecessary. The only difference is that the customer will have a choice over packages and CAN save money. If you compare the two, different customers can save different amounts of money or end up spending more. Just like cellular plans, you pick whichever provider and plan works best for you, and theres a lot of competition so you have a healthy selection to choose from.
Again, bandwidth that you use for certain services are universal, the ISP doesn't spend any money giving the client a universal connection to all the services. This isn't cable, in where the company that provides you the cable owns the network of channels that are broadcast. I should not pay more to access another section of the internet because the provider doesn't spend any more resources providing the client with connection to any certain website.
Then you can pick a different ISP that might charge less for their gaming package, if say you're a gamer and you want to fully utilize the gaming services. You'd still end up paying for it anyways in the universal package, its just since you're only given a net fee of all the services combined you can't actually see how much you're paying for each package that exists inside the universal plan.
All that you described existed already before net neutrality ended, it was just entirely centralized so you didnt have to worry about percentages and individual package fees. Now that net neutrality exists there's more you have to take into consideration in whichever plan or ISP you decide to go with, but its still the same fees.