(1) Choose no permission - Then, if you want you can go to your photos in the iOS Photos app, select a few, pick "Send to App -> Facebook" when you want to give Facebook a few photos
(2) Copy and Paste photos
(3) Choose "only selected photos" - In this case, in the Facebook app, you choose to add photos, the photos you previously gave the app permission to view appear and there's a button "Select more Photos". You can pick that and select more. I use this option peronsally
(4) Choose "all photos" - I give this permission to Google Photos since I use Google Photos to make all my photos visible across all devices.
If you choose 4, that just seems on you. You told them they could access all the photos.
iOS you can
(1) Choose no permission - Then, if you want you can go to your photos in the iOS Photos app, select a few, pick "Send to App -> Facebook" when you want to give Facebook a few photos
(2) Copy and Paste photos
(3) Choose "only selected photos" - In this case, in the Facebook app, you choose to add photos, the photos you previously gave the app permission to view appear and there's a button "Select more Photos". You can pick that and select more. I use this option peronsally
(4) Choose "all photos" - I give this permission to Google Photos since I use Google Photos to make all my photos visible across all devices.
If you choose 4, that just seems on you. You told them they could access all the photos.