Vierling jumped three levels in one year, you'd expect some regression at the ML level, but his BB rate at both AA and AAA suggests that's a better indicator going forward, same with his K rate. Moniak hasn't shown much improvement in that area, which suggests he'll be more vulnerable at the ML level where pitchers can exploit his overly aggressive approach.
Not saying Vierling is a star in waiting, but watching him and Maton, both have good compact swing mechanics, something I look at with young hitters, long swings might work in the minors but are exposed at the ML level. A compact swing allows you an extra tenth of a second to recognize the spin on a ball.
I don't see Vierling in CF, rather, part of a LF platoon. It would be nice if Haseley got over his personal issues and rebounded, I don't see Moniak in the majors to start 2022. Muzzoti is at least a year away, Rojas two years.