You can make avatars rectangular by changing the following css in templates/base/css/default.css:
.bx-def-thumbnail {
border-radius: 3px;
-moz-border-radius: 3px;
-webkit-border-radius: 3px;
}
It will change it almost everywhere.
You can also use another template from the market, when it will be some for 7.2 version.

You can re-arrange block on profile page from admin panel > builders > pages builder. Users can re-arrange own profile's blocks with help of 3rd-party modules - see more http://www.boonex.com/m/Profile_Composer_2010_08_11

You need to switch to "Embed" option on video upload page and insert youtube link.

Most modules from 7.1 should be compatible with 7.2, I think that developers will update their's mods compatibility when 7.2 release will be available. But it is always better to ask particular author. There is also a community list of compatible modules:
http://www.boonex.com/forums/topic/Module-proven-do-work-with-Dolphin-7-2.htm