Well because we bought land with water, power and driveway already in, I did all the checking up as well as submitted the BSA but my builder is going to handle the rest of the permitting from here on out. Is that your question? How much you will need to do once you hire a builder? I would imagine it would depend on your agreement with your builder. For example, our builder said we could do all the permit stuff, which might save some money but cost us in time and stress.

Around here, it's the surveyor who obtains the permits after
creating a site plan. I'm happy with this arrangement, figuring
that county officials would rather work with fellow professionals
than deal with an ignorant layman.

If your doing fixed price, I think it will be less fun unless your plans and specs are extremely thorough, you dont make many changes and you dont choose the lowest bidder.

I told my architect that I wanted to go through
however many design iterations it would take to arrive
at plans that would require no changes. Yes, the problem
then will be how to evaluate builders beyond just
looking at their quotes. In government software
projects, with which I'm familiar, proposals are
rated some percent on price and some percent on
the quality of the technical approach. For the latter,
I'm guessing that a personal interview might serve
as the equivalent for builders, who are probably more
at ease talking than writing.

A good builder might not be a good salesman. Look at their finished projects and talk to the owners and the architects. Be sure they will work well with your architect. Your architect should be assisting you with this process.

"Fun" it won't be. The selection stage is the stage which is most fun for most people---until it gets to be too much of a chore picking out stuff that you had no idea needed to be picked out. The construction phase can be "exciting" terrifying" or even "challenging", but "fun" isn't a word most people associate with handing over gobs of cash for a giant hole in the ground and which doesn't turn into a recognizable structure without more gobs of cash being handed over. Spending money on such a large scale involves a huge element of trust, and most people aren't that trusting, so it scares them to death. Unless you are a gazillionaire who has someone selected to supervise the build completely with all of the headaches included and all you have to do is to show up occasionally with your entourage for an in progress tour. That might be fun!