On the subject of a congregant being free to leave the shul if he doesn’t like the Rav; We have to understand the history of this halocha. When the poskim discuss appointing a Rav, or a kehilla appointing the son of the previous Rav, It was the Rav of a town. Historically, a town had a Beis Haknesses. And the Rav was the town Rabbi, who was therefore the Rav of the shul by default. This situation hardly exists nowadays.
As an example, Gateshead is a town, with a Rav and, until recently, a single shul. Of course there are many minyonim in the town, Boarding School, the yeshivos and kollelim, but all are under the auspices of the Town Rav. And regarding membership, all shomrei shabbos residents of the town are automatically members of the kehilla, and therefore obligated to pay membership.
The modern day, sha’alo is about appointing the son of the previous Rabbi of the shtiebel, and if I don’t like him, I’ll daven in the shtiebel on the next corner. Or as the situation is in many places in the US, where the Rav is called the Mara D’Asra of a single shul, and of the members of his shul.