Where Prince of Wales and Repulse go without Force Z

If Force Z had not been sent, would Prince of Wales and Repulse join the Eastern Fleet during the Indian Ocean raid?

Yes; they would likely join the Eastern Fleet because they were the major ships available for reassignment.

The question removes the historical Force Z deployment and asks whether Prince of Wales and Repulse would appear during the Indian Ocean raid. Both ships would become part of the Eastern Fleet. They were historically sent where they were because they were the major ships judged available rather than already committed elsewhere. The alternative therefore redirects the same available capital ships into the developing Indian Ocean force.