The main split in Christianity (Between Catholics and Protestants) is the issue of WHO tells you what to do and HOW they tell you.
The Catholic Church has staked out the "chain of evidence" theory which is Sacred Tradition. The Church has all authority in Faith and Morals.
Protestants (since Martin Luther) cling to the assertion that the Bible alone can give instruction directly, or; Sola Scriptura. God speaks to each individual through bible study alone.
Sola scriptura was a foundational doctrinal principle of the Protestant Reformation held by the reformer Martin Luther and is a definitive principle of Protestants today
Sola scriptura may be contrasted with Roman Catholic and Eastern Orthodox teaching, in which the Bible must be interpreted by church teaching, by considering the Bible in the context of Sacred Tradition.
Wikipedia
Jehovah's Witnesses claim to be NEITHER Catholic nor Protestant.
The methodology for learning Jehovah's will, however, is interestingly split over time in official orthodoxies.
Charles Taze (Pastor) Russell applied himself, as so many of his generation did, to reading the Bible and using a concordance. He attended lectures by all sorts of Millennialst preachers. He combined his own personal tastes with what he heard and read to produced his magnum Opus: STUDIES IN THE SCRIPTURES.
This is clearly a Sola Scriptura approach.
However......Maria Russell interpreted her Bible reading into what has become a cornerstone doctrine of the Faithful and Discreet Slave. Her husband eventually was won over to it. The result of her idea amounts to creating a bifurcated combining of Sola Scriptura with Sacred Tradition (or Majesterium) to make an enlightened go-between the mouthpiece of God.
Pastor Russell protested against the religious teachings of his parent's which included hell, Trinity, election of the saints, self-perfection. Wouldn't this make him a Protestant protesting against Protestantism? Such persons are called Apostate.
Russell's apostate tastes in End of the World/Christ Returns mania turned him away from mainstream churches. He stumbled on to the last vestiges of the William Miller fallout with Christendom. Christ was supposed to return in 1843/44. Nothing had happened. Rather than admit error, the more obstinate fringe zealots sought to patch up their systematic explanation of prophecy. Russell liked one of the patches when he saw it: Miller had been correct! Jesus DID return; only INVISIBLY! Russell set to work patching the patches together into a do-it-yourself-explanation of how Jehovah had planned the whole thing from time immemorial. The result: Studies in the Scriptures (or, Divine Plan).
DIVINE PLAN OF THE AGES was advertised and touted as the superior methodology for enlightenment. It was topical and contained step by step chains of reasoning which amounted to personal theology of Russell's.
AUTHORITY TO JUDGE an individual, at the time of C.T.Russell was in the hands of Jesus Christ alone. Christ was considered as already returned, reigning invisibly and judging each Christian before Armageddon in 1914.
Responsibility devolved to judgement: if you warned others (Russell's version of the warning, not William Miller's) you'd be favorably judged. If you failed to warn others you were blood guilty before Armageddon's judgement.
When Armageddon did not arrive as expected; the time of the end extended into a grace period which became an opportunity for further doctrinal assessment in the hands of Russell's un-appointed successor, Judge Rutherford.
Gradually Rutherford re-vamped Russell's infrastructure and re-interpreted the Maria Russell doctrine of Faithful and Discreet Slave to apply to the Watchtower board members (in reality; only Rutherford!).
Over time, this has been further re-vamped into further refinements, changes and reinterpretations.
Today, Jehovah's Witnesses don't deal with Jesus Christ as their judge so much as they deal with a board of Directors. A Governing Body of anointed are the core messege-bearers and mouthpiece of Jehovah. This leaves very little for Jesus Christ to accomplish! The mouthpiece has a monopoly on Bible reading vis a vis correct interpretation and orthodoxy.
Each individual Jehovah's Witness member is judged according to compliance with the Policy mandates from Brooklyn New York.
Consequently, Jehovah's Witnesses are judged by self-appointed special agents who have assumed the role of the Papacy in the Catholic Church. When the Pope speaks; a true Catholic must listen and obey. When the Governing Body speaks; the true Jehovah's Witness must obey.
The Catholic Church will excommunicate dissidents. The Watchtower Organization will disfellowship obstinate members.
Further, and strikingly, in recent years; the Watchtower Organization has further narrowed its definitions to the point of accepting Calvinism as its core ideology. Calvinism teaches that only the elect go to heaven and only the elect have the benefit of the Holy Spirit in Salvation and bible understanding. Jehovah's Witness Governing Body anointed ones are the only ones the Bible is directed at.
Jehovah's Witnessess have created 2nd class facilities for non-anointed (non-elect) persons on Earth under the judgement and direction of the Elect.
There has been a long, slow evolution since C.T.Russell attended Adventist lectures and sought to avoid Hellfire and the Trinity. His wealth and commitment to his own vision of Truth gave him enough momentum to take advantage of the disaffections of many people who did NOT wish to be wrong in believing Christ would Return in 1843/44 as preached by William Miller. The Great Disappointment left thousands of people in the lurch who had either left their mainstream church or had been kicked out for contrary teaching. When C.T.Russell came along and "improved" on Miller's doctrines of Christ's imminent return; they snatched at it in a heartbeat.
Who could have foreseen that over 100 years later it would amount to a small band of senior citizens ruling over a vast empire of true believers in excess of 7 million souls? Yet, in reality, that is what the Watchtower Society amounts to. People who are contrarian in view who don't want to admit the mainstream churches might be right still insist Jesus Christ is already among us playing second fiddle to Brooklyn New York's ever-changing doctrines and explanations of a 2,000 year old Jewish book.