Cellular and GNSS Antennas

So if my impedance is less than 50 ohms, can I just decrease the width? I know it's probably harder to calculate, but wouldn't that theoretically work?

This is the sort of problem a VNA is needed to solve.... RF test equipment for microwave frequencies is not
cheap.

Some means of evualating the trasmitted power can help tune up a transmitting antenna, but
for reception direct into a chip you only have whats on the chip to help diagnose...