document library – Best way to store Images in SharePoint Online

You have several topics to address.
Let’s start with the data volume.
You will need to use tools to upload such a data volume in a reliable way. Using File Explorer or OneDrive for Business (ODFB) client will not work.
For example, 3 TB of images each consuming 5 MB storage corresponds with 600000 files. This is beyond the limit of ODFB client.

In addition, not many tools support extracting of EXIF metadata during uploading.
OOTB SharePoint does not expose EXIF metadata directly and the values cannot be used for searching, viewing and filtering. Using Power Apps / Power Automate it is possible to expose/extract EXIF properties after uploading but firing off 600k Power Automate flows does not sound attractive to me.

There are migrations tools that extract EXIF metadata (and other metadata schemes like XMP, IPTC, ICS) during uploading and capture them into SharePoint columns. See e.g. here (all the EXIF metadata listed in the bottom section can be extracted and stored in SharePoint columns). The SharePoint columns can then be used for searching, viewing, filtering etc..
The tools can also be used to extract the location from images with GPS details. Some tools also support GeoTagging to set location details for files without GPS details during uploading.

The choice for a library type (picture, asset, …) depends on what you want to do with the images after they have been uploaded.
See What is the difference between Document Library, Picture Library & Asset Libray? for a similar discussion.

Hope this helps,

Paul | SLIM Applications