I am not a kloxo expert... But have been trying to learn it as quickly as possible. I would answer your questions as this:
Kloxo-MR has made it quite simple to do everything you want. Mustafa has made it as simple as click which webserver you want, it works. It supports nginx proxy to apache.
I would suggest install on a fresh server/vps. Follow the install instructions - it is simple and easy.
The DNS template manager is easy to use... easiest I have used next to cpanel. I am sure whatever your needs are concerning you sites won't be a problem.
I think a fresh install uses anywhere from 250-350 MBs memory complete. Thats for everything (mail server, mysql, kloxo, etc) so not too bad - its not completely lightweight, but it is full of functions and in my opinion "pretty damn simple to use"

You don't have to pre-install anything. Except the requirements in the install instructions... yum-utils, yum-priorities... etc.