What parts of Protestantism accept that there are some on earth who 'smite the earth with plagues' till the end of time (Revelation 11:6)? And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth. These are the two olive trees, and the two candlesticks standing before the God of the earth. And if any man will hurt them, fire proceedeth out of their mouth, and devoureth their enemies: and if any man will hurt them, he must in this manner be killed. These have power to shut heaven, that it rain not in the days of their prophecy: and have power over waters to turn them to blood, and to smite the earth with all plagues, as often as they will.
[Revelation 11:3-5, KJV]

This passage makes reference to Moses turning the waters of Egypt to blood, to Elijah deliberately praying for an extensive three and a half year long drought in the Mediterranean region and to Elijah also calling down fire from heaven to consume troops of soldiers sent by a king to apprehend him.
What parts of Protestantism accept that such men still walk the earth, perhaps not in every generation, but from century to century and that these 'have power ... to smite the earth with plagues' ?
And what parts of Protestantism accept that such men will continue to be seen to the end of time, since their duration is 1,260 days which is three and an half years ( or 'weeks' in the prophetic aspect) and since that length of time prophetically indicates the duration of the Church Age from the ascension of Christ until his triumphant return ?
When it comes to interpreting Revelation in general, and those 4 verses in particular, I consulted a book where the Protestant author classifies 4 main ‘types’ of interpretation. He explains what he means by those ‘types’ at the start of his book, summarized on the cover jacket as: “PRETERISM: most prophecies were fulfilled during the time of the Roman empire.  HISTORICIST: the prophecies have been fulfilled throughout history and are still being fulfilled today.   FUTURIST: most prophecies are yet to be fulfilled.  SPIRITUAL (or Symbolic or Idealist): most prophecies portray ongoing cosmic conflict of spiritual realities and may have many fulfilments throughout history.”

For the various Christian authors he quotes and their sources, please consult the book “Revelation – Four Views – A Parallel Commentary” edited by Steve Gregg, page xiii (Nelson, 1997).  My compilation comes from pages 226 to 233. But as it really is the Futurist and Spiritual interpretation groups of Protestants who hold largely (though not entirely) to the views you ask about, I will only state some of their views.  If you would like to have similar notes I compiled on the other two groups, please just let me know and I will e-mail them to you.

“The Futurist” view taken by Walvoord claims that the 1,260 days of verse 3 says that as “the two witnesses pour out divine judgments upon the earth and need divine protection lest they be killed, it implies that they are in the latter half of the seven years when awful persecution will afflict the people of God… The punishments and judgments the witnesses inflict on the world also seem to fit better in the great tribulation period.”  Others with that general view (Lindsey, Morris and Ryrie) differ regarding the time period, thinking it is the first one, adding that it seems to be the coming of the beast onto the scene in power that terminates their witness.  

Most Futurists take the 2 witnesses to be actual men who will arise to prophesy in Jerusalem in the Tribulation.  Some think they will be Moses and Elijah themselves.  Others think that it is Elijah and Enoch (the view of the earliest apocryphal writers and the early exegetes of the church, a view shared by modern writer Henry Morris.)  On the other hand, Mounce writes, “It seems more likely… that they are not two individuals but a symbol of the witnessing church in the last tumultuous days before the end of the age.” 

Others think that two individuals are the principal interpretation of the expression, but also leave room for the possibility of including a larger group of witnesses in the picture, including Gaebelein: “Perhaps the leaders would be two great instruments, manifesting the spirit of Moses and Elijah, endowed with supernatural power, but a larger number of witnesses is unquestionably in view here.”  Ladd takes this approach as well, allowing that Possibly there is a blending of the symbolic and the specific in the passage. He believes the witnesses to be two “actual historical eschatological personages who will be sent to Israel to bring about her conversion.” He elaborates that the two witnesses may indeed represent the witness of the church to Israel throughout the age. This witness, however, will be consummated in the end time by the appearance of two Christian prophets, who will come in the spirit of Moses and Elijah, even as John the Baptist came in the spirit of Elijah. 

This is apparently Ironside’s position as summarized by Charles Ryrie thus, “…this much is certain (1) They are persons, for all the other times that the word ‘witness’ is used in the NT it is used of persons. They are not movements or powers, but individual persons. (2) It is also certain that they are not named in the text, and this writer feels that the case should be left there. These are two exceptional witnesses raised up by God during the Tribulation and preserved by Him until their ministry is completed.” Walvoord comes to a position similar to Ryrie: “It seems far preferable to regard these two witnesses as two prophets who will be raised up from among those who turn to Christ in the time following the rapture.”

“The Spiritual” view holds that the two witnesses represent the witnessing church throughout its entire career. Hendriksen says, “These witnesses symbolize the Church militant bearing testimony through its ministers and missionaries throughout the present dispensation.”  Regarding the miracles, Leon Morris writes, “God’s servants in the new dispensation have just as great resources as did Moses and Elijah in the old.” The deadly fire pictures those setting out to destroy them being undone.  Lenski writes that “the word in the mouth of the Lord’s prophet-witnesses may be scorned but it is not an empty sound. Its judgments are fire that devours its enemies.” The failure of Julian the Apostate to reimpose paganism in the ‘christianized’ Roman Empire is cited as an example.

I have not sorted out any particular denominations these various authors belong to, and it might be fair to say that within all the denominations they represent, there will be some people with differing views.