Per Baseball Savant:
Vaz is better at framing and pop up time (Plawecki is 99th out of 102 players).
According to FanGraphs:
Vaz has made 46% of unlikely plays for his career (expectation is 10-40% likelihood). Plawecki is only at 20%. Hands, release, arm strength and arm accuracy.
Vaz is 2nd overall in dWAR. Wong is ranked AHEAD of Plawecki in dWAR. Connor Wong!
Overall, Vaz has better CERA numbers than Plawecki by a good margin. However, you can come up with a SSS that fits your narrative that all of these metrics are baloney and that only CERA on a pitcher by pitcher basis matters because somehow a micro sample size tells you the real story.
By any reasonable measure Vaz should remain the starting C.