So I've tried to read everything I could on these forums on touring bikes and equipment and how they relate to how much you carry.

It seems that touring exists on a continuum.

You can do credit card touring where you carry almost no load (couple water bottles and maybe a energy bar.) This type of touring you can do on almost any bike.

The other extreme of touring is totally self-supported touring. Here you carry a tent, food, water, etc. With this type of touring it seems best if you have a specially designed bike. This type of bike usually has 36 spokes, a longer chainstay, etc.

Where I'm a bit confused is with the idea of ultralight touring or bike-packing.

Is there some rule of thumb that says, 'If you are carrying more than X pounds you should have 36 spoke wheels?

At what point in the tour planning should someone say, 'Ok, I better get a 'real' touring bike.'