According to what “Go64” shows, all parts of Nik Collection version 6 are “universal” and should therefore run on Apple Silicon Macs without Rosetta. Note: Not tested/verified it yet on Apple Silicon Mac.
The new collection definitely cannot be installed side by side with other (recent) versions of the Nik Collection. The Nik apps require additional resources that the installer puts into
/Library/Application Support/DxO/
Remove or rename this stuff und the apps will “quit unexpectedly”. This also means that there is no way to upgrade and fallback - except through the respective (un)installers.
Because of this, even a test drive can trash your trusted Nik install. Make sure you have an installer for the version that has proven to do what you need! All who have paid license(s) for the “Nik Collection by DxO” should find the respective installer(s) in shop.dxo.com.