Can't speak about Retool but I wouldn't want to go away from standard software development life cycle with version control, release management and testing... And I definitely would want to avoid a proprietary platform. Isn't there an open source alternative?
We evaluated PayloadCMS to drive the backend of a mobile app and eventually settled on Directus because it supported heterogeneous collections which was something we had to have.
Directus also has a template for a multi-tenant app which sounds like something you might need.
Can't speak about Retool but I wouldn't want to go away from standard software development life cycle with version control, release management and testing... And I definitely would want to avoid a proprietary platform. Isn't there an open source alternative?