Opportunities for the implementation of the bundle: Website - CRM - personal account of the client?

Question

CRM

I am looking for a programming solution (language, logic) for the competent creation of a technical specification for a project with subsequent placement on freelansim.ru
Need: implementation of a client’s personal account, accessible to him from a browser from various devices and a mobile application and from CRM - from our side.
That is, you need to implement a bundle: a website (a form on the website, registration) - a user's personal account (access through a browser and a mobile application) - CRM.
As options:
- a personal account module for a certain CMS, accessible from a third-party CRM
- a separate personal account that is not connected to the main site, accessible from a third-party CRM
- a personal account implemented within the CRM, for example, by providing custom access to individual fields in the card client.
- any other solution
The goal is two-way interaction with clients through a personal account from CRM.
As an additional more complex option - the development of a personal account constructor (its structure in the form of the ability to add personal fields, integrated with CRM).
Interested in existing opportunities for such an implementation.
I thank everyone who will respond.