Looking for CRM (FinTech industry) with some requirements

Hi!
So All the last 2 days I tested so many CRMs but I didn’t found the one that actually help me, and I would like to get your experience with that

So I have few requirements that really important for me:
1. Full and fast RestApi.
2. Manage and create custom modules.
3. Manage relationships between modules.
4. Full permissions system.
5. Open source on demand.

Thanks!