Which CRM to choose for SaaS service? And how to integrate with it?

Question

CRM

Which CRM to choose for a SaaS service with installation based on paid subscriptions and paid one-time actions on the site?
I am considering integrating the site with vtiger crm to make it easier to track the effectiveness of site promotion and advertising.
Do I understand correctly that when registering on the site, I have to send the client card to crm via api. When replenishing the balance, also send something to CRM, when performing any paid action, also send data to CRM?
That is, send any sneeze to CRM after copying there almost everything related to billing on the site?
Is there too much data going into CRM?
Will CRM start to blunt from this?

Answer 1

We are a SaaS service and use our own solution.
Here you can see what the interface looks like:
https://ozma.io/ru/
Here are the integration details:
https://wiki.ozma.io/ru/docs/fundb-api
If there are difficulties - write. We'll help you set it up and show you how it works

Answer 2

We use Amo but are not very happy

Answer 3

as a pseudo-crm, you can use a regular google spreadsheet. You did not indicate what functions you expect from crm, so if we are talking about collecting information and further actions with it, then the table is enough, you can send rest requests to the table that will replenish it, and the table itself is able to send requests to third-party services, including your site or server, etc. There are restrictions on storing information, but I don’t remember a single project where it even got in the way