Thank you OK645 for your good explanation!
As to your specific question (assuming you're speaking NG here)...
I'm speaking about the classic but I suppose it's the same as in the NG?
And how is the profile computed if we don't put the VNAV cruise altitude on the FMC? Imagine we "just" use LVL CHG and not VNAV...
Let's say we are on a 8Nm downwind (HDG SEL and ALT HOLD and the FAP is on top of the leg page with the correct intercept course) and the VNAV deviation indicates 2000ft high ... How is this value calculated?