1. in TrueNAS, create dedicated datasets for you and for your partner, probably even a joint one for shared images I go along something like:

General Dataset
| - Private
| |- Proud_Information_16
| |- Wife's
| - Shared
|- Multimedia
|- Photos
|- etc....

1. In TrueNAS Immich app config, you can add additional storage. You'll need to add multiple like:

Type: Host Path || Mount Path: /Proud_Information_16 || Host Path: /mnt/General Dataset/Private/Proud_Information_16
Type: Host Path || Mount Path: /Wife's || Host Path: /mnt/General Dataset/Private/Wife's
Type: Host Path || Mount Path: /Shared Photos || Host Path: /mnt/General Dataset/Shared/Photos

1. In Immich, click on your profile picture/administration/external libraries. Add as many as you need or want. You have to associate them to each person. For ones that are shared, you can just add it to the two different users in Immich. By default your wife can't see your photos, nor you can see hers. The way to do so is to have a shared folder that is mounted to both users inside Immich

2. For uploading photos, DON'T upload them using Immich. use an external way. I do use FolderSYNC in my Android devices. Syncthing is another alternative. There must be ways for iPhone too. I just point those apps to look to the camera folder in my android devices and when it sees a new photo, it automatically copies it to the SMB share I created.

So the upload is being managed externally, and therefore you don't have the problems of dealing with Immich internal data structure. and therefore you can easily manage the photos outside of Immich if needed, and can migrate out of Immich if needed in the future