Some thoughts about product owners. First, it's best to have one PO per product, not per team. Otherwise you have a cacophony of conflicting decisions with no coherence. The teams can each have somebody in the role of "on-site customer," though. 1/7

That person can answer questions that come up during the course of development, talk to other customers if necessary, &c. It's best if that person is an actual customer. Otherwise, you're playing a game of "telephone." The teams also need to understand the business. 2/7

If there's a business person on the team, their role is NOT to "represent the business," it's to teach business thinking to the team. They are not an intermediary. They're a team member with a specialized skill that they're infusing into the rest of the team. 3/7

Other specialists (e.g. architects) work the same way. They don't do the architecture. The teach the team to do architecture and help coordinate between teams. 4/7

I'll point out that, if you're unfortunate enough to be doing Scrum, this way of working is perfectly aligned with the Scrum Guide. At no point does the guide say that you need a 1:1 between teams and POs. All it says is that here's a PO on the team. 5/7

That PO can be on several teams. 6/7

A single product backlog is always best, not a plethora of them. "The Product Owner is the sole person responsible for managing the Product Backlog." One backlog. One PO. 7/7