For wireframing, I decided to use Keynote instead of just hand sketching. I did supplement with vectors made in Affinity Designer however. But for the most part, my screens were made in Keynote.
Although colors are limited, the drawing type/tools and customizing objects are intuitive and quite rich. In fact, the shapes include lots of useful icons, like cameras and maps. This allowed for creating clean layouts with visual hints quickly.
Keynote gets two thumbs up from me for wireframing!