I don’t have a specific recommendation, but can shed some light on official support.
Day-to-day and static monitoring can be done on a smaller screen than setup. If you want to permanently display a fullscreen graph, 7" can work just fine. Editing the brewery builder on anything less than 15" is terribly finicky right now.
Right now anything smaller than 1600 x 900 (15" laptop) is supported on a best-effort basis.
The next goal is to fix all issues at 1368 x 768 (13" laptop). This will likely happen the next few weeks.
Perfect mobile / touch screen support will likely take a while. Neither of us has a background in UX/UI design. There’s a lot of trial and error involved.