Correct all our templates use the built in flex menu.
* The main menu position isn?t really a module position in the traditional sense, the site menu is hard coded in the menu position and it cannot be replaced with a different menu from another module by publishing to the "menu" position.
Correct its not a position but built in. You could custom code a module position to be in place of this menu to use any other menu system you desire.
* If you put a menu elsewhere, it can only be tire accordion menu. The accordion menu is a menu for a sidebar as it does not have a horizontal display mode.
Correct, unless you use a 3rd party menu
* This template only allows use of the built in main menu, the standard Joomla menu or the S5 accordion menu and does not allow any 3rd part ones like CKmenu
We haven't tested but the only thing that would prohibit it would be JavaScript conflictions with the menu.