Best Tool for Viral Waiting List Growth

Hi! I'm advising on a startup on a new B2B SaaS product and we are rolling out a waitlist launch strategy while we're still in beta. I've traditionally used in house tech or lead gen forms a la Typeform, but was interesting in trying out something like getwaitlist.com (or other tools) to create an incentive to move up the waitlist based on the # of people. Or alternatively trying Typeform + Viral Loops. Anyone have a tried and true solution they love?