I have a comic that I converted the first couple of pages to vertical format.
Some tips include pacing and dialogue. I ran across a lot of dialogue that had to be manipulated a bit to fit vertical. The max in a vertical balloon is usually two sentences the most. Some of my panels had to be cut in creative ways to accommodate that.
Also, spacing between panels seems to be a controversial thing. The majority is that there should be more space while some believe there is less. Pick what works for your story.
I have since decided to switch back to traditional due to time contains. I also want to collect the pages and print a book one day. So I rather focus on story telling in that format for now.