Can one limit the display size of images in posts? Can I specify the maximum width of images as 720 px?
I initially created my phpBB 2.0.19 as a https site (and upgraded to 2.0.22 and AttMod; can I re-create a phpBB installation in http and merely copy over the entire directory and expect it to work, i.e. carrying over all files, posts, attachments, memberships, etc with it?
So long as you change the board settings to reflect the non-https status I don't see why not. Use phpMyAdmin to backup the database though since the backup utility in phpBB doesn't backup the attach mod tables.
You can specify max dimensions of images in Special Categories in the ACP.