I'll take a shot at this, expecting others to chime in.
The standard MTO is essentially ordering a particular style you like on an existing last.
For example, using G&G for reference, you could choose a style and have it lasted on the MH71, TG, DG and so on.
From my experience, my example works for EG, Bonafe, Carmina etc.
TRUE bespoke is having a maker create a last specifically for you.
This method will normally take a couple of fittings with test shoes so the...