How do you say "person who ____" or "person who is _____" in Japanese?

You are asking how to form a relative clause in Japanese.

English uses relative pronouns that simultaneously act as conjunctions introducing the relative clause, such as: who, whom, which, that. Relative clauses in English, even though they function as adjectives, come after the nouns they describe, unlike true adjectives.

Japanese takes the opposite approach. There are no relative pronouns, and relative clauses come before the nouns they describe, just like true adjectives.

person who [verb] --- becomes: [verb - in the plain form] person (who - is not actually stated; there is no need for it, since the relative clause must describe person, the noun that follows)

Your update is beyond my intermediate ability to translate accurately.

another example:

I saw the person who always talks a lot. = (as for me) much talks person saw.

(boku wa; watashi wa, ore wa; atashi wa etc) takusan hanasu hito wo mimashita.

It seems strange at first, but is essentially far easier than English relative clauses.

OK, I try to make this as simple as possilbe.

person who do/does ～するひと　（I presume you understand verb conjugations)
person who is ～いひと　(い、as in the end of adjective. Also I presume you know how adjective changes)

example

person who runs はしるひと
person who eats たべるひと
person who write かくひと　　

person who is busy いそがしいひと
person who is cold つめたいひと

These are basic ideas, and I am sure there are some exceptions... but if you make mistakes in conjugations, it will be perfectly understandable, though, you will not sound like native.