Please resolve this question -

I installed ubuntu 16.4 lts with its LAMP stack.
I now want to install OC. Which package shall I use: owncloud or owncloud-files????

OR would it have been better to install Ubuntu WITHOUT the LAMP stack and then install OC (and if so, what OC package?????)?????

Normaly you can install the package "owncloud". This package is the full installation of ownCloud and installs also an apache2 Server and the required PHP-Modules. It should will work if you already installed a LAMP Stack.
You can read more about the packages here.