Hello, this is Emily.
I want to point out something very important here. It depends on how your photos are set up with OneDrive and Google One, there's actually one scenario your photos can be deleted from Google One if you delete them off OneDrive.
I urge that you do the following first.
If you have OneDrive app installed, click on the cloud icon on the bottom right on taskbar and go to Settings.
Go to Manage Backup, on the pop up, make sure all folders, especially the Pictures folders is turned off.
Then you can go to the Account tab and click on Unlink this PC.
After you unlink your PC, there's a chance your photos are gone in the Pictures folder. If that's the case, go to www.onedrive.com via the web browser, and download them manually from there.
Once the above steps are done, you can safely remove them in www.onedrive.com.
The reason I don't want you to do so is in case your OneDrive syncs with your local Pictures folder, and your Google is synced to your local Pictures folder as well. In that case, deleting from OneDrive will indirectly delete from Google via the local Pictures folder.