The original "style" of worship was the liturgy (RC calls it the "Mass").
That the early church had a developed liturgy by the second century is attested to by the statements of Justin Martyr.
Justin Martyr: (AD 100-165) The First Apology of Justin
Chapter LXVII.—Weekly Worship of the Christians.
…… (1) And on the day called Sunday, all who live in cities or in the country gather together to one place, and
(2) the memoirs of the apostles or the writings of the prophets are read, as long as time permits;
(3) then, when the reader has ceased, the president(1) verbally instructs, and exhorts to the imitation of these good things.
(4) Then we all rise together and pray, and, as we before said, when our prayer is ended,
(5) bread and wine and water are brought, and the president1 in like manner offers prayers and thanksgivings, according to his ability, and
(6) the people assent, saying Amen;
(7) and there is a distribution to each, and a participation of that over which thanks have been given, (the Eucharist) and to those who are absent a portion is sent by the deacons………….
Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Saviour on the same day rose from the dead. For He was crucified on the day before that of Saturn (Saturday); and on the day after that of Saturn, which is the day of the Sun, having appeared to His apostles and disciples,
(8) He (Jesus) taught them (the apostles & disciples) these things, which we have submitted to you also for your consideration.
Justin described a gathering
(a) of the entire local church,
(b) at a place which would accommodate them,
(c) on Sunday.
He then described the process of the meeting which are easily identified as:
A. the Liturgy of the word
(1) The reading of the Gospels or Prophets
(2) The sermon
(3) The prayers of the people
B. The Liturgy of the Eucharist
(4) The consecration of the bread and wine (by the presider, AKA: "priest")
(5) The “great Amen”
(6) The people receive the Eucharist
The source of this form of liturgy:
Justin stated that it was Jesus who taught this form of worship.
Thus, Justin refuted the modern notion that the "Mass" was a later development.
What Justin describes is the basic format of the liturgy that is followed to this day in all Orthodox, Roman Catholic, Lutheran, Anglican, Coptic and Assyrian Churches.
-----------
1. The “president” refers to the presiding presbyter or the overseer. The word “presbyter” or “elder” (presbuteros) has come down to us in modern English as “priest” and the word overseer (episcopos) has come down to us in English as “bishop.”