Since there is no ruling body for evangelical Christians, each church, preacher, and member could take a different interpretation. In this answer I'll present various articles from generally well-known evangelical sources which provide contradictory answers, to give an idea of some of thing things that are believed amongst evangelicals.
In some cases, they believe both the 144000 and the multitude are the same set of people, and in other cases they don't. Where they believe them to be different, I've tried to explain what they believe both groups are.
All emphasis is quotes are my own.
Pre-millenial Example
This article from GotQuestions (whose Statement of Faith appears consistent with Evangelicalism) appear to hold the pre-millenial view
It is true that there will be people ruling in the millennium with Christ...Furthermore, the millennium is different from the eternal state, which will be established at the completion of the millennial period
They understand the 144000 to be a specific set of Jews at a particular time:
When taken at face value, Revelation 7:4 seems to speak of 144,000 actual people living during the end-times tribulation. Nothing in the passage leads to interpreting the 144,000 as anything but a literal number of Jews
And they (quite strongly!) disagree that it is a literal interpretation of the full number of saved Christians:
Much of the confusion regarding the 144,000 is a result of the false doctrine of the Jehovah’s Witnesses [who] claim that 144,000 is a limit to the number of people who will reign with Christ in heaven and spend eternity with God
But the 144000 are not the multitude described in the rest of the chapter. Instead, this group of Jews goes on to convert large numbers of Christians, and it's these that the multitude is talking about.
As a result of their ministry, millions—“a great multitude that no one could count, from every nation, tribe, people and language” (Revelation 7:9)—will come to faith in Christ.
Contradicting pre-millennial example
John Piper, a well-known US evangelical preacher, describes himself as pre-millenial. This article referencing Revelation 7, directly contradicts this view, suggesting they are not converts from the tribulation.
Unless you restrict this multitude to the converts of the great tribulation and say that God's missionary purpose then is different than it is now, the implication of God's worldwide purpose is clear
Instead, he appears to suggest they represent all Chritians. This is backed up by his use of the words "saints" in this article, where he appears to equate both the 144000 and the multitude to all Christians.
in dying [Jesus] ransomed a great multitude of saints from all the nations
suggests Piper is using the word "saints" to mean "all Christians", which he then equates to both the 144000 and the multitude.
Then before the opening of the final seal John is given a vision of the destiny of the saints in all this upheaval. In 7:1–8 he sees that they will be sealed by God on the earth so they are preserved for his own. Then in 7:9–17 he sees them in the final triumphant state in heaven as an uncountable multitude from every nation serving God in security and joy forever and ever.
A-millennial example
This article is from the Gospel Coallition, which describes itself as "a fellowship of evangelical churches". It is written by Kevin DeYoung, who in another article for TGC describes himself as a-millennial. He also appears to interpret the 144000 as a representation of all Christians.
The 144,000 are not an ethnic Jewish remnant, and certainly not an Anointed Class of saints who became Jehovah’s Witnesses before 1935. The 144,000 represent the entire community of the redeemed.
I take it that, if the 144,000 represent all of God's people, DeYoung is interpreting the whole of Revelation 7 as referring to the same group of people.
Post-millennial Example
I haven't been able to find a great example for this. This article is from someone describing themselves as post-millenial, although doesn't seem to refer to themselves as "evangelical". It's not clear who they think the multitude are, but they draw a strong distinction between them and the 144000, which suggests they don't believe it is a particular set of Jews, at the very least.
The 144,000 saints represent Jewish converts to Christianity who dwell in Israel...John distinguishes them from “the great multitude, which no one could count, from every nation and all tribes and peoples and tongues” (Rev 7:9). John is careful to make this strong distinction between the two groups.
Summary
Evangelical Christians generally disagree over the interpretation of who the multitude are, who the 144000 are, and whether they are the same set of people. Even Christians who appear to hold to the same interpretation of Revelation in general disagree over this passage in particular. However, there is a vague notion that suggests the most common interpretation is that it represents all of God's people.
Edit:
I'm tempted to say that the question of whether this multitude has not yet received life is a separate question, but I'll attempt to answer it anyway. If others feel it should be split out, then I can copy this section of the answer across.
Revelation 7:17 mentioned two things happening: God wiping every tear from their eye, and them being led to the water of life. It seems you've interpretted this to mean that they don't yet have life, and will only receive it when they reach said water of life.
However, if we look later in Revelation, we find that both phrases are used to describe the New Creation. I would therefore interpret these verses as simply telling us in advance, before the trouble we're about the see through Revelation, that this multitude will reach the New Jerusalem.
Then I saw “a new heaven and a new earth,”[a] for the first heaven and the first earth had passed away, and there was no longer any sea. 2 I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband. 3 And I heard a loud voice from the throne saying, “Look! God’s dwelling place is now among the people, and he will dwell with them. They will be his people, and God himself will be with them and be their God. 4 ‘He will wipe every tear from their eyes. There will be no more death’[b] or mourning or crying or pain, for the old order of things has passed away.”
5 He who was seated on the throne said, “I am making everything new!” Then he said, “Write this down, for these words are trustworthy and true.” Revelation 21:1-5 (NIV®)
And
Then the angel showed me the river of the water of life, as clear as crystal, flowing from the throne of God and of the Lamb 2 down the middle of the great street of the city. On each side of the river stood the tree of life, bearing twelve crops of fruit, yielding its fruit every month. Revelation 22:1-2 (NIV®)
