I’ll give you the basic meaning of each of the words in question, and then point out a couple of hermeneutical issues that might help.
(1) “Nation” is the Greek ethnos, which simply means “a race, a people of a particular nation” like the Samaritan nation or people (Acts 8:9) or the Jews (Acts 10:22). Compare also the seven nations of Canaan (Acts 13:19), nation rising against nation (Mark 13:8). It may also be used in the sense of “foreigners” as an equivalent of the Hebrew goyim. It was actually used in Rome of the foreign people in contrast to Italians. So in the New Testament it is sometimes used in the sense of heathen, Gentiles, pagans in contrast to the Jews who had the promises of God (cf. Matt. 10:18).
Further, it is used of Gentile churches which would mean churches made of primarily non-Jews of many different nations like Greek and Italian, etc. Ultimately, the context must be carefully noted.
(2) “Kindred” or tribe is phule mean “a tribe” or “a nation, people.” Again context is the issue. It is used of the twelve tribes of Israel or of a specific tribe of Israel (Rev. 7:4; Heb. 7:13), but it may also be used of a nation of people (Matt. 24:30; Rev. 1:7). In some cases it would, because of its combination with other synonyms, perhaps focus on smaller groups within a particular nation of people.
(2) “Tongue” is glossa and means “a tongue” or “a language” and as such, becomes a synonym for a group of people distinguished by their particular language or even dialect.
(3) “People” is laos and means just that, “a people, a crowd, a populace” or of “a people as a nation.”
In the passages of Revelation like 5:9; 7:9; 10:11; 11:9; 13:7; 14:6; 17:15, these words are combined together to emphasize the concept of totality or all-encompassing, i.e., “all the world.” It stresses that no group of people will be left untouched or affected in some way, depending on the context. In Revelation 14:6, it refers, of course, to the outreach of the gospel and in 5:9 to the extent or unlimited nature of the death of Christ. So in essence, each passage where these words are used either by themselves or with other words as synonyms, the context must be looked at carefully