Build a Zoho creator app for allied health administration

We would like to build a zoho creator app that will help us with the administration side of our small allied health business. I have started setting it up and can do the basics myself (basically creating the 'forms') however have no experience so would like someone to help with the more difficult parts. It is a little difficult to describe the job given my lack of experience with what is actually possible with zoho. The particular components we need are: Waitlist - Tracking the clients on our waitlist, the services they would like, whether their intake paperwork has been completed, triage notes from therapists, and communications between the bookings team. Service agreements and support plans (essentially contracts and quotes) - A form that can be filled out by admin and signed by the client. It includes a detailed quote of the services and requires a bit of maths/formulas. We are currently using an excel spreadsheet to produce this (which I can share), however it is too difficult for our clients to understand so we need something that is simpler to read but is still capable of calculating maths for all of their services over a year. I.e. it should hide fields that are irrelevant to that client. Current cases - A spreadsheet of all of our current clients, which is linked to the 'service agreement and support plans' above - after a client is signed on, they go to this spreadsheet so that we can track both their agreement (expiry etc) and additional details. Additional details include who their therapists are, when we need to complete reports for them. I would also like help to work out what sort of subscription is best for us, as I am confused between the difference of 'users' and 'portal users'. Ideally, I would like to explain the type of access each staff member needs, and you can tell me what subscription would allow that. E.g. I want to make sure staff can't accidentally delete entries, but they CAN edit them. Additionally, I need support to ensure that the app is secure privacy wise as it will contain private/confidential health information. As mentioned, I have been able to build the very basics of these forms (basically inputting the fields needed) but I would like help for the more complex parts such as connecting them and creating formulas. Please feel free to ask any questions!