Your right! It is a real challenge to open your phone and say "cancel my reservations" . Strongly sugest don't consider RVing/camping on the west coast but I suspect it would not be your choice to consider anyway!
We've camped on the left coast before, went up the 101 all the way to Olympic actually. And we used our standard method of limited reservations and had zero 'we're full' responses. Of course we made reservations for Yosemite North Pines and for Lassen Volcanic. We visited Crater Lake and Rainer along with Olympic during that trip.
Our original and early plan this year, was for PNW for North Cascades and the eastern sides of WA and OR with a dip into CA to Lassen Volcanic. As the year moved on that became impossible.
Some of the problems with canceling or changing reservation is playing phone tag with the cg people. Some cg operators are very hard to get on the phone. We have rarely changed dates but have not canceled any recently. In my experience you can forget doing either thru reserveamerica or rec.gov. We did that in the past and never saw the actual promised refund.
And as the first law of Engineering goes: if it ain't broke then don't fix it. Our method has worked for probably close to 100,000 miles of RVing in mostly the western states but going to every one of the lower 48 with our kids and Mexico and Canada as well.
If your method is as successful then carry on, I won't try to talk you out of it. Some people like to minutely plan every step of a trip and others prefer flexibility. Neither method is better and the whole point is to have an enjoyable time. So continue with whichever makes you happy.
500 mile days included. Actually we used to do longer days when I was still working pre-retirement, went from Florida to Yosemite in 4 1/2 days one year when car trouble delayed our start. But now with more time we prefer a slower pace.