Effectively yes. When installing a different operating system the old is overwritten hence the need to save your data (images, recordings, contacts etc) maybe to an SD card that has been formatted as an external drive. Then after the change of OS you can reinstall from the SD card. You can use a computer to do the save and transfer.
As to actually using the ‘E Easy Installer’ goes I have no idea I use the default Android 10 without a Google account etc.
And what Google knows Google and Microsoft and all others know and it won’t go away ~ they have the data now. What you can do is to have as little data connection as possible, but that often means being a little bit more hands on with the options mentioned in the previous posts. I can’t be that bothered, I’ve more entertaining things to do than worry to much about what data Google is gathering.