Yes, both Miro and NinjaMock offer a Free Trial.
Miro is designed for Large Enterprises, Medium Business and Small Business.
NinjaMock is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing for Miro Starts at $8/User/Month when Billed Yearly whereas for NinjaMock Starts at $7.69/Month when Billed Yearly.
Some top alternatives to Miro includes Collaboard, Microsoft Whiteboard, WhiteboardFox, Conceptboard, MURAL, Lucidspark, Whimsical, Board, Zoom Whiteboard and Witeboard.
Some top alternatives to NinjaMock includes Miro, HotGloo, Pidoco, Balsamiq, Wireframe.cc, Wirify, Claritee, Stage, Mockup Clips and Zen Wireframe.