I mainly use my iPhone for filming and the iOS camera app because it’s the fastest to get running out of my pocket. You might be interested in this post about using Filmic from the lock screen
My phone doesn’t have iCloud photos on and my iPad does. This allows me to choose which media backup in iCloud. iCloud photos wasn’t designed for video making and is too slow for transferring source material for video and to watch old video projects.
I airdrop from phone to iPad via an archive file. When the iPad receives it the iPad asks you which app to use. You can choose the Files app and save directly to the LumaFusion/UserMedia folder without them being added to the Photos app. Here’s a shortcut for sharing media to an archive
https://www.icloud.com/shortcuts/746da4 ... 65438ad6d4
I also use an SD card reader to transfer media mainly when I film with a video camera to get long zoom shots. LumaFusion will read files directly from an SD card but it’s usually slowish and I usually use the Files app to copy the files into LumaFusion/UserMedia.
Note that LumaFusion will also make a temporary copy of any media you use in a project until the project is deleted. Another thing people regularly have trouble with is that any files deleted by LumaFusion or the Files app are at first just moved to Files/RecentlyDeleted for about 30 days. The system will permanently delete them earlier if space is required but otherwise they will still show as LumaFusion memory usage. You can manually delete files in RecentlyDeleted to release memory immediately.
People also use external drives to transfer media but I’ve never felt the need to and prefer to keep my gear as small as possible for travel. I make lots of videos but they are usually short (1-3 minutes) but with lots of roughly 3 sec clips. Your requirements are probably different.