the problem with perimeter/layer numbers and thickness is that different slicers do it differently.
Some let you set and actual thickness - say 0.8mm.
And some let you set the number of layers.
So you need to know the diameter of your nozzle and the thickness of the ;layers you are printing.

If you print at 0.3mm layer height and with a 0.4mm diameter nozzle.
then:

3 top and bottom layers = 3x3 - 0.9mm 'skin' on the top and bottom of a model
3 perimeter shells - 3x0.4 - 1.2 mm walls/perimeters/shell around the sides of the model and ALSO around any holes in the model.

Print at 0.1mm layer height and to get the same top and bottom skin thickness and you need 9 top & bottom layers.

I find that a 2.75 mm hole will print slightly smaller than 3mm bolt and will be a tight and snug fit.

It's also best to screw in once and then leave it. If you repeatedly screw the bolt in and out you will eventually wear the threads away and each time you remove and re-insert the hold is slightly less.

I also add a drop of uhu all purpose glue to theb hole prior to screwing the bolt in. Best glue for pla I've found.

Why isn't nylon used more by home 3d printer owners.
because it can be a total bastard to print with.

It's really stringy, so print speeds and retractions ahve to be slowed right down. It expands when hot and shrinks when cooling so can be a bugger to get to stick to stuff.
And the good stuff - ie: that shrinks less and prints easier - is comparitively expensive.

The two best nylons I've tried are: Mymat nylon, which is about as good as it gets. No shrinkage, prints clean and sticks to just about anything.
And taulman nylon 230.

Like eevry type of printing filament - not all nylons are the same.
Most of the cheap stuff out of chine is really bloody difficult to use. And requires higher printing temps and an enclosed build volume.
So you tend to go for the more pricey - but easier to use taulman products. They - literally - have a nylon for all occasions.

Then there's the fact that nylon is pretty soft. So for many uses pet-g is an excellent and easier to use alternative.

And these days a fairly stiff polypropylene is not only cheaper but just as tough and much much easier to print with.

Books wise - well, people tend to find that they can make more money recording youtube videos these days - so technical books on 3d printing have almost dried up.

The one I bought - about 8 years ago, was excellent and covered everything from software to machines, as well as designing and modifying designs.
But the chap has not updated it and whiole the basic information is still valid, the details are all well out of date.
https://www.amazon.co.uk/Practical-3...7722000&sr=8-3

One of the problems is the sheer speed that ALL aspects of rapid prototyping and 3d printing is advancing.
Back when I got my first machine - you had abs and pla. And pla was considered weak and brittle - took me 6 months to realsie that was wrong - even then.

Now - 8 years later, you can pick up a printer for under £100, there are dozens of different types of material to print with and the technology of the machines themselves has moved forward so fast that a book printed last year would be out of date less than a year later.

I like books I grew up learning from books and I still prefer to have a book in one hand and the computer mouse in the other.

But 3d printing is one of those things where there is no substitute for trial and error.
It's a lot more user friendly than when i started, but soceity has become ncreasingly more impatient and people don't believe they have to actually 'learn' anything to be able to use tools any more.
For that we have smart phones to blame. When you make a complicated product that has no manual - not only do most people never use a fraction of the devices capabilities - they assume that nothing else 'needs' a manual either - so they just get out of the habit of learning HOW to use things.

Anyway - rant over :-)