" 2)  You suggest shortening or lengthening the coax cable to adjust the
SWR."

This is a BAD idea.  What you are doing with this procedure is "tuning" the
cable/antenna combination to a single frequency.  You still have standing
waves on the cable even at the tuned frequency which results in radiation
from the cable which mostly horizontal.  This is wasted RF power.  The goal
must be to install an antenna which has less than 2/1 VSWR over the entire
frequency band referenced to 50 ohms. Connect it to the comm set with a 50
ohm cable and you will have less than 2/1 VSWR at the cable over the entire
frequency band.  You do not want a tuned cable.  You want a flat cable
(electrically speaking).
Bob Jude, N65BJ
I am qualified to comment on the subject --- 40+ years in antenna and RF
equipment design and test.