Presbyteros (or oi in the plural) does NOT mean Priests.
Here is the meaning of that term
1. elder, of age,
1. the elder of two people
2. advanced in life, an elder, a senior
1. forefathers
2. a term of rank or office
1. among the Jews
1. members of the great council or Sanhedrin (because in early times the rulers of the people, judges, etc., were selected from elderly men)
2. of those who in separate cities managed public affairs and administered justice
2. among the Christians, those who presided over the assemblies (or churches) The NT uses the term bishop, elders, and presbyters interchangeably
3. the twenty four members of the heavenly Sanhedrin or court seated on thrones around the throne of God
The word for Priest is Hiereus and it refers to all believers.
Regarding the congregational part/ it is hole (holos)ekklesia. Translated correctly, WHOLE CHURCH.
Ekklesia means
1) a gathering of citizens called out from their homes into some public place, an assembly
a) an assembly of the people convened at the public place of the council for the purpose of deliberating
b) the assembly of the Israelites
c) any gathering or throng of men assembled by chance, tumultuously
d) in a Christian sense
1) an assembly of Christians gathered for worship in a religious meeting
2) a company of Christian, or of those who, hoping for eternal salvation through Jesus Christ, observe their own religious rites, hold their own religious meetings, and manage their own affairs, according to regulations prescribed for the body for order's sake
3) those who anywhere, in a city, village, constitute such a company and are united into one body
4) the whole body of Christians scattered throughout the earth
5) the assembly of faithful Christians already dead and received into heaven
It does NOT mean some elite group; rather, the passage speaks of the "MULTITUDE" and the "WHOLE CHURCH". It is congregational and does involved the participation of laity.
Another time Paul uses this exact phrase in 1 Corinthians 14 If therefore the whole church be come together into one place, and all speak with tongues, and there come in [those that are] unlearned, or unbelievers, will they not say that ye are mad?
You are not suggesting that he is speaking of some hierarchical authority there are you?
"Presbyteros" can mean all these things, but in Christian usage its primary meaning is "priest", from which "priest" is derived. "Hieros" is primarily pagan or Hebrew priest. I don't think it was ever used as a Christian priest; got a patristic source?
It does NOT mean some elite group
In Matthew 18 it does, because it makes a disctintion beteween an appeal to a group of fellow believers and the Church as a whole. One meaning is not exclusionary of the other, as indeed, "church" can mean the entirety of the believers as well. Context rules, not the dictionary.