SaaS Architecture Advisory for No-Code Solution

I need architect advice for a no-code/configurable enterprise SaaS currently under development. It will have multiple modules, with each module purchased separately. Please advise on:

1. Multi-tenancy: Should we use Hybrid Multi-Tenant architecture? Compare shared DB/schema, separate schema, separate DB and hybrid approaches considering GxP, security, scalability, performance and cost.

2. Customer/Site model: A corporate customer may have 10+ branches/sites, each with different electronic processes. Should the hierarchy be Customer → Sites → Modules → Processes → Users? Should sites be separate tenants, sub-tenants or part of one tenant?

3. Environments & DB: Each customer may require DEV, VALIDATION and PROD. For a customer with 10+ sites:

- How many DBs are recommended?
- Should each environment have a separate DB?
- Should sites have separate DB/schema?
- What should be shared vs isolated?
- Can a tenant/site be backed up/restored independently?

4. No-code configuration: What architecture is best for configurable forms, workflows, business rules, roles, approvals, e-signatures, notifications and reports? How should configuration versioning, audit trail and DEV→VALIDATION→PROD promotion work?

6. Modules & services: Should we use modular monolith, microservices or hybrid? How should independently purchased/enabled modules be architected without excessive complexity?

7. Infrastructure: What is the most cost-effective cloud (AWS/Azure/GCP)? Do we need Kubernetes initially? Recommend VM/container/Kubernetes strategy and when to scale.

8. Security: Recommend tenant/site isolation, SSO/MFA, RBAC, API security, encryption, secrets/key management and protection against cross-tenant access.

9. Database & storage: Recommend DB technology, object storage for GxP documents, caching, messaging and audit-log architecture.

10. Backup/DR: Recommend backup, retention, RPO/RTO, DR and independent customer/site restore.

11. Scalability & cost: Recommend architecture for 1, 10, 50, 100 and 500 customers. When should a large customer move to dedicated DB/infrastructure?

12. Final: Please provide a practical target architecture/diagram and clear recommendations for tenancy, DB, environments, cloud, Kubernetes, security, GxP and cost, optimized to start small and scale globally without major redesign.