Moving SharePoint On Prem to cloud

How big is your organisation?
Within What industry ?
What SharePoint on-prem are you sitting on currently ?
Are you international ? etc etc

My recommendations is to create a whole new structure from scratch using hub sites, sites, teams and Yammer for discussions! Microsoft has a pretty good guide on how to think and plan

https://learn.microsoft.com/en-us/sharepoint/intranet-team-overview

What is going to take the most part in a project like this isn't the technical part but the change management, creating a superuser network and maintained.
A modern intranet in SharePoint is usually owned by several stakeholders within the company

The root site will be the home of your organisation,  so recommend setting it as home site in the SharePoint admin, Also recommend using the built in viva connection app in teams, you can rename something more fitting if needed.

As for migration, I really really recommend that you first setup your information classication first and clean up before moving any files. Files that are going to be kept can me migrated with ShareGate or Microsoft Own tools! (ShareGate is Faster in my experience).