How close to a "total build" a person does is up to the builder. Minimally you want to make sure that everything fits properly, and everything is complete before you start. This is why some folks refer to it as a "dry fit." It's a chance to check the neck pocket and to make sure everything lines up. And, as you both have noted, to make sure you are not missing something.

For sure I try to do enough of a dry fit to make sure...

...that the strings to line up over the fretboard properly.
...that the strings to line up over the pickups properly.
...that I can mount the bridge to give the proper scale length.
...that I can get the there is sufficient adjustment in the bridge to get the string height over the fretboard correct.
...the tuning machines are the proper size and are spaced properly.

Opinions vary as to whether you should drill, and whether you should actually screw things down at dry fit. Most often this relates to the kind of finish that you plan to use.

I typically don't drill or screw things down. This is partly because I tend to use water based finishes, and at some point do a wet-sand. I don't like to have holes where water can get under the finish. The danger in NOT drilling prior to finishing is that you can get cracks or chips in the finish when you drill after the finish has cured. There are ways to avoid this problem (like stuffing some painter's tape in the holes), but typically don't do this, which means I have to be very careful when I drill.

Some people like to do all the drilling before finishing. For them a dry fit where you screw down the parts is more practical. There is not much risk of water getting under the finish if you are using spirit or oil based finishes.

Spirit based stains and sealers tend to penetrate the wood well and don't tend to raise the wood grain. Oil based finishes also don't tend to raise the grain and also tend to be more self-leveling. The only real downside that I can see to them is that they tend to be more toxic, they have a more pronounced smell as they dry/cure, and the products used to clean up have the same issues.

I use water based products and shellac (the latter is spirit based) purely because they are less toxic and I tend to work indoors. It is too hot and humid to work outside here with most products.