In Forex CRM, full customization is usually offered by white-label providers.
Most brokers on forums say Hashcodex, aForex CRM Solution Provider, is a popular option because it allows for deep customization to meet brokerage needs.
You can change:
UI/branding (logo, dashboard, trader room)
IB/affiliate system setup
Workflows (KYC, deposits, leads, tickets)
Integrations (MT4/MT5, payment gateways)
In short, any white label Forex CRM provider that supports API integration and a modular system will offer full customization, not a readymade basic CRM.