What is the best way to merge storyboards with other users? Do you just build dynamic layouts?

There's definitely no "best way", it just depends on the product you're building. With that being said, I prefer programmatic layouts vs storyboard. If I HAVE to use storyboard with a team, it requires careful planning. Generally, we'll keep a one-to-many relationship between devs to storyboards. I may have ownership over 5 storyboard screens but ONLY I have ownership over them. That way, merge conflicts are heavily minimized.