This answer really depends on what plan you have selected even though I believe even a free plan would be able to handle 100 visitors on a landing page especially if it has limited work flows. For further clarification on this check out this information from Bubbles FAQ
What happens when I go viral?
Bubble handles scaling your app automatically behind the scenes. You can purchase additional server capacity with a single click, with no need to worry about provisioning servers or databases in advance. Our shared infrastructure is designed to dynamically allocate resources as needed to support web-scale applications, and we also offer dedicated hosting solutions for apps with custom requirements.
There are no hard limits on the number of users, volume of traffic, or amount of data you want to store. We support your growth from baby MVP to grown-up internet-wide phenomenon.