My go-to strategy for visiting the parks in the summer has been to be there for rope drop and do a bunch in the morning, eat lunch in a/c, head back to our on-site resort for rest / swimming during the hottest hours of the afternoon, and then return to the park in the evening. However, with the early magic hour now a 1/2 hour and extra magic hours no longer open to us because we are staying at CBR rather than a deluxe, will this strategy still work, or will the back and forth travel eat up too much time? We're planning a visit in June or July of 2024 so heat will definitely be an issue.
It depends. Everything is relative. I think the strategy will work, but you might have to compromise a little here and there to make it work.
For one thing, heat, as you likely know, is only part of summer weather at WDW. Storms are also a factor. Maybe you get lucky (few storms), or maybe storms = limited swimming.
We don't yet know what 2024 park hours will be. Taking breaks is easier when the park hours are longer. When there are frequent parties at night and short park hours, then it is harder to take breaks. One compromise is to pay for the PM party or after hours events, I suppose.
Another compromise is to shift how many rides or which rides you cover. Maybe swap a few long-wait attractions for short-wait attractions here and there.
Shortening your commute time by paying for faster transportation is another option. I tend to like to have a car myself, and find it is often faster to travel by car than WDW's transportation, but the benefit is variable. If we don't have a car, we still pay for periodic transportation where it offers the most help.
Still one more is to take shorter breaks. We jokingly quote the Tiki Room from time to time, "My siestas are getting shorter and shorter!"
Ultimately, you have to do what makes the most sense of course.
One more option is a split stay. Spend most of the trip at CBR, but one night at a hotel that costs less (offsets cost of transportation), or one night at a deluxe hotel (=easy walk to one of the parks). To make split stays work, we tend to not unpack much at the short stay. Maybe pack a daybag that has all you need for that one night.