Subscribers and premium users can use the forum's image attachment mechanism to attach photos to posts.
Subscribers and premium users are not required to use that mechanism, just in case there is any uncertainty in anyone's mind about that. It is simply available to them for their use.
Subscribers and premium users can post pictures by linking to them, also. If you prefer that so you don't have to resize images, that is fine. It is a service for those who do not have photo hosting accounts elsewhere.
One thing photo linking also allows is that standard users can post photo ads for free.
Subscribers and premium users are not required to use that mechanism, just in case there is any uncertainty in anyone's mind about that. It is simply available to them for their use.
Subscribers and premium users can post pictures by linking to them, also. If you prefer that so you don't have to resize images, that is fine. It is a service for those who do not have photo hosting accounts elsewhere.
One thing photo linking also allows is that standard users can post photo ads for free.