If I remove all data from my iPhone...

If you restore the device, or you sign out of iCloud before deleting anything then yes, data will be saved on iCloud.

If you manually delete stuff, while still signed in to iCloud, changes will sync and deleted items that are also in icloud will get deleted there too.

See here, to correctly wipe the iPhone without deleting data from iCloud: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

If you are syncing things like Safari bookmarks, and contacts to iCloud, then the answer is yes. These sorts of items still will be synced to iCloud.