For apps removal I like free AppCleaner app. If you no longer want to keep the data, move it to trash and empty the trash.
If you want to keep data, move it to an external drive or cloud storage. iCloud is not a cloud storage/backup solution. After you get the data to an external location, delete it off your internal drive.
A relatively easy way to remove all your user data quickly is to create a second Admin account, login to it and removed your old user deleting Data and the Home folder. Of course you now have new user login.
One thing to be wary off, and this is on the newer OS versions, deleting a massive amount of data will likely cause MacOS to create a temporary dataset named "Purgeable Data". Give it a couple of days and your Mac will release it. There are apps to do it more quickly. Purgeable Data looks unusable, it's not, it's available it's just your Mac will release it when needed.