Yes, both Proto.io and UXPin offer a Free Trial.
Proto.io is designed for Large Enterprises, Medium Business and Small Business.
UXPin is designed for Individuals, Large Enterprises, Medium Business and Small Business.
Pricing for Proto.io Starts at $24/Month when Billed Yearly whereas for UXPin Starts at $19/Month when Billed Yearly.
Some top alternatives to Proto.io includes Figma, FigJam, UXPin, UX-App, Justinmind, UserX, UXArmy, UX Metrics, MockupTiger, Fluid UI and Framer X.
Some top alternatives to UXPin includes Figma, FigJam, Adobe XD, UX-App, Justinmind, UserX, Axure Cloud, UXArmy, UX Metrics, Axure RP and Proto.io.