whati kind of people is the company popular with?

主语既然是PEOPLE的话，就不要用the company popular with了
What kind of people is the most popular/welcome in this company?

whati kind of people are the company popular with

is在这里没有错，应该是单数。
这句话应该是没错的。

没错 没错

What kind of people is popular in the company?

错了， 你到底想说什么？