Here is evidence for plurality of elders:
(5) The consistent pattern in the NT is that every church had several elders.
Note the following texts (where either elder or bishop is used):
Acts 11:30--elders at the church of Antioch
Acts 14:23--Paul and Barnabas appoint "elders in every church"
Acts 15:2, 4, 6, 22, 23; 16:4--elders at the church in Jerusalem
Acts 20:17, 28--elders/bishops at the church of Ephesus (v. 17--"elders of the church")
Acts 21:18--elders at the church in Jerusalem
Phil 1:1--the church at Philippi has bishops and deacons
1 Tim 5:17--elders at the church of Ephesus
Titus 1:5--Titus is to appoint elders in every town7
Jas 5:14--"the elders of the church"
1 Pet 5:1-2--"the elders among you"
***This said, I believe if a pastor moves into a new position in which he is the sole pastor...there is no reason to quickly appoint other elders who might not be qualified or even understand their role. Taking the time to teach and train elders would be much better.
That said, I do think the plurality of elders functions within a congregationalism...
Biblical congregationalism is about affirming, appointing, and submitting to qualified leaders. Each established church is responsible for affirming the call of and appointing the men who fill leadership positions in the church (Acts 6:1-7, 1 Timothy 3:1-13). But they affirm and appoint trustworthy men who they then submit to and follow (Hebrews 13:17).
Biblical congregationalism is about confirming who belongs to the body and who does not. Matthew 18 and 1 Corinthians 5 contain those passages we often use in reference to “church discipline” but there is so much more going on there. That whole binding-and-loosing in heaven thing, it all has to do with recognizing who belongs to Jesus and who does not based on a person’s testimony in combination with a person’s life.
This is why if a person is walking in sin and they refuse an individual and 2-or-3 person rebuke, you take them before the church. It is only the congregation then who, after pleading for their repentance, has the right to rebuke them in such a way as to say, “You are like a Gentile and a tax collector to us.” In other words, “You are a sinner who has shown that you do not belong as a part of this body because you have not truly turned to follow Jesus.”
“Where two or three are gathered in my name” tells us the congregational body, no matter how small or large, has an authority the individual Christian does not: to say to someone, “You belong, welcome, my brother/sister,” or, “You do not belong, turn from your sin and follow Jesus.”
(from: http://sbcvoices.com/what-is-congregationalism-biblically-speaking-2/ )
As to which group (Elders or congregation) have the final say...I would tend to think that a congregation should have the ability to remove unfaithful Elders, since it is they who appointed them...BUT If the elders are plural, and functioning well, they can hold each other accountable and remove any offending elder themselves. I would not have a problem serving in either type of church. Legally, it would depend on the church charter/constitution/bylaws as to which group could legally kick out the other group, or claim ownership of the building.
I do think local church autonomy is biblical...
And...I think that a sole pastor who has complete authority without being able to be removed by some congregation or elder board is unbiblical and dangerous.