Teams caches everything, and a machine that had both versions stores it twice

Teams is the clearest example of a Windows pattern worth knowing generally: when a vendor rewrites an application, the old application's data usually stays on the disk.

Find both sets

Get-ChildItem "$env:APPDATA\Microsoft\Teams","$env:LOCALAPPDATA\Packages\MSTeams*","$env:LOCALAPPDATA\Microsoft\Teams" -EA SilentlyContinue |
  ForEach-Object {
    $s = (Get-ChildItem $_.FullName -Recurse -Force -File -EA SilentlyContinue | Measure-Object Length -Sum).Sum
    [PSCustomObject]@{ MB = [math]::Round($s/1MB); Path = $_.FullName }
  } | Sort-Object MB -Descending

The classic client lives in AppData\Roaming\Microsoft\Teams. The newer one is a Store style app under AppData\Local\Packages. A machine that has been through both has both, and only one of them is being written to.

Telling live data from leftovers

Get-ChildItem "$env:APPDATA\Microsoft" -Directory | Sort-Object LastWriteTime -Descending |
  Select-Object LastWriteTime, Name -First 10

A folder last written to months ago belongs to a version you no longer run. That is the one to remove. A folder modified today is the client you use, and clearing it is a cache decision rather than a cleanup.

What is safe in the live one

• Cache, Code Cache, GPUCache. Disposable, rebuilt on launch.
• Service Worker. Disposable, resyncs.
• Logs. Safe, and usually small.
• Local Storage and IndexedDB. These hold your session. Clearing means signing in again.

Quit it properly first

Teams keeps running in the notification area after the window closes, and clearing folders under a running Electron app achieves very little because it rewrites them immediately. Quit it from the notification area icon, not the window's close button.

The wider pattern

Any application that has been through a major rewrite is worth checking for a second data folder. The same shape shows up in Slack and Discord, and the general map of where this lives is AppData.