With your specifications and expectations - there is no point even looking at a Mac-Mini or MacBookPro as you will spend more time failing to make things work...
You would be MUCH better off with a MacPro, which will also give you the facility to take video input successfully.
You mention not getting a reliable spec all the time... and having to re-prep.
It may be worth considering taking an HD with you with your own installation of MacOS that you can use on any other intelMac server. We use the same disk image on 2007-2011 servers. At least you know its configured correctly. (just watch out for peripheral drivers)
S