Well its all a matter of taste as we know. I happen to like the portal look of Photopost.
If you set your screen table width to 80% and expect things to be perfect then thats just plain impossible web design or not. In fact the majority of web sites out there use 95-100% table width. Just a plain fact. I have to absolutely hate 80% width or fixed width sites so its all relative here.
The simple matter is if your going to try running a fixed width or small width site yes you might need to tweak things as displaying the sheer amount of data generated is impossible without tweaking things to your needs.
Example the prev and next thumb box's you would never be able to use on a 80% width site if your using the sidebar on showphoto. Just food for thought. Thats why I personally only use the sidebar on the index because of all the data and admin links etc in showphoto.
We have documentation on what templates are with what scripts in the documentation forum and as for where to edit templates you can do so by hand which is my favorite way or you can use the template editor in the admin section. Which Templates for What--FAQ?