[garzabla]

There is no connection between the P&ID/Line List & Isometrics
Therefor the answer to nearly all of your other questions is No

The only way to estimate the total number of Iso’s required is to apply an average of 2 to 3 Iso’s per line number but this will only be a rough initial estimate. If you feel your estimate is inflated that is why. There is no way of knowing the exact number until the isometric extraction is finished.

PDMS does not determine the number of Iso’s, that is the job of the Piping Designer