Could you explain a little more about what your app does and the experience for each business?
If you’re using Google Sheets, you may start to experience slowness beyond 25,000 rows. However, if you use Glide Tables then these limits are much, much higher.
I would also suggest reading the pricing page thoroughly and thinking about Public v.s Private. I suspect you’ll want to limit access to your app via email – which is only possible on the private plans. https://www.glideapps.com/pricing