Varsho will definitely be the starting CF in 2024-26. His playing time there in 2023 will depend on a bunch of factors (injuries, performance of KK, etc) but I suspect he will be playing all the OF positions in 2023. If they platoon KK, then Varsho likely plays CF against LHP. On the days Springer is at DH and KK is also in the lineup, then they likely move Varsho to RF. And so on.
As far as the trade, as long as Varsho is a 3-4 WAR OF that can cover CF, then I don't think the Jays are going to regret the deal even if Moreno turns into a star. Outfield up and down the organization was a weakness. They needed someone, especially at CF, long term. The fact that they got 4 years of that type of player was definitely worth the gamble, IMO. If Varsho has another gear in him offensively, then even better.