iCloud will store iOS backups and restore them. iCloud offers a COMPLETE backup of your files, not only photos videos, contacts and calendar contrary to other backup services. iCloud will restore your iOS the way it was before including application data all in ONE operation. Restoring from iCloud will result in a complete restore of all the apps present on the device at the time to the backup. You don't want to have to remember which apps were on the device and download them again manually, one by one.
Apple offers 5 GB of free space to anyone with an AppleID. The $ .99 you're paying now gives you more space only, not better or more options. At one dollar a month it's a real bargain. So, no, you will not lose Find my iPhone or any other sync service like Contacts, Calendars, Reminders, etc, as long as they are active in your iCloud settings.
I doubt Google Drive oneDrive or DropBox for all their qualities offer phone support in case of trouble.
https://support.apple.com/en-us/HT207428