Jeffers was 8th (worst) in the AL with 5 passed balls last year. Sandy Leon was 6th worst with 6. 5 or 6 passed balls is maybe 3-4 runs per season at most.
There were 2487 stolen bases league wide last year, 1/2 of a stolen base per team per game, that result in on average .3 of a run per steal. Jeffers had 31 steals on him, so that’s 10 runs estimated in the season.
There are 100+ pitches thrown per game, getting a higher percentage of strikes impacts dozens of outcomes per game. Jeffers is ranked 21st (best) in the league. Improved counts puts at-bats in the pitchers’ favor.
I think Jeffers is a high quality half of a catching tandem. The question is the other half. Narvaez seems like a good option. The Twins also have Banuelos, a good journeyman at the Saints but doesn’t hit, is supposed to be an excellent fielder. And Bechtold is progressing nicely (but doesn’t really hit either)
if the rest of the lineup hits, Carlos Correa and a corner outfielder, DH… a black hole at catcher for half your games could be overcome.