It really comes down to how much the Twins believe in Garver as a starter this year and next.
If they see him as a back up, go for Realmuto. If they see him as a starter, the one year guys would be a great addition to split time with him in his rookie year. There is so much to learn and so much more prep work at catcher.
They should not count on Castro as a reliable solution as a starter next year.
I tend to agree with this. Garver is a rookie and not playing daily. Why? Because Molitor doesn't believe in him? Or because Molitor is letting him grow and develop instead of thrusting him to the daily job? If it's the former, may be time to pony up. It takes quality to get quality. In fact, I'm wondering how the Twins will be able to hold on to some guys in regard to next year's 40 man and rule V draft. If Molitor actually likes the game calling and potential of Garver, then a better veteran to split time and learn from makes the most sense.
Could the Twins offer and afford to part with Gonsalves and Gordon to Miami? Absolutely. Would it hurt? Absolutely. Which means it sounds about right with another piece thrown in.