Question

[#1]

Are you able to work with more than one freelancer on the same project?

[#2]

re: "Are you able to work with more than one freelancer on the same project?"

Yes.

Many projects involve a client working with more than one freelancer.

As a client, I often hire multiple freelancers using the same job posting.

The highest number of freelancers I have hired using the same job posting is about 20. But Upwork places no limit on this. You can hire as many as you want to.