Need Suggestions in implementing Employee Experience using MSOffice 365 tools

Hey Everyone, 

I'm eager to develop a universal portal for certain users, resembling a webpage with a more intuitive user interface and a more robust user experience. What pre-built solutions within the Microsoft Office 365 suite could facilitate this?

I want to host it as a Desktop application as well as a website.

As per my analysis:

1) Sharepoint Online  - A better handy solution - But I need to customise a lot. Not a ready made solution.
2) Power Pages - I dont have much knowledge on this one.
3)  Viva Connections - It does solves those problems. But it mainly depends on MS Teams. I need it  to be detached from Teams.

Thanks in advance !