I'm in the same boat. We're relying on the EOR to get CEC points for PR as well. My wife recently finished her studies and will be applying for a PGWP. I've been on a SOWP, working through a Canadian EOR company for a U.S. company for over a year. I get paid through the EOR, receive paystubs, a T4, and an employment letter with their name and address. Essentially, they are my legal employer, and I'm being paid and paying taxes while living in Canada. Based on what my immigration lawyer advised, as long as the Canadian PEO provides paystubs, a T4, and an employment letter, it should work.
We're considering a similar setup for my wife since she received an offer from a U.S. company that has no presence in Canada. The company is open to hiring and paying her through a PEO company that handles EOR. That said, I've seen many online posts with people expressing uncertainty about this, which has made me a bit doubtful as well.