Google photos

Yes. You can't instruct Google Photo to upload all the photos to iCloud. As long as you have them on a cloud service, why do you want them to also be on iCloud? You can access them from any iOS device you have as well as your computer through Google Photos.

Any photo you want to save, hold your finger on the photo and the option to save it will appear. This will save it to your iPad photo library, which will save it to iCloud.