I have used both the XXL LCD for my printer (Robo3D) and the Full Graphics LCD for the MP CNC. They both came from ebay sellers but I don’t remember which right now. The smart LCD that you list has the same functionality and firmware requirements to the XXL LCD, the only difference is in the display module size. These LCDs are so simple that you probably can’t go wrong with cheap one from ebay. The only problem I noticed is that the quality of the rotary encoder my Full Graphics one is not as good as the XXL. It sometimes oversteps a menu item as I scroll down.
For $10 plus shipping I would go for the regular Smart Display Controller. Yes, that #define looks like the only one you need to uncomment.
Does the Full Graphics display give you any advantages over the text display? I found a graphics display version for about the same cost here. The text version I listed above would probably get here quicker since that is coming from NJ & this graphic display is shipped from China.
No the Full Graphics LCD really has no advantage. It has fancy icons for the hot end and bed temperature and the cooling fan status which are only needed for a printer. They also make the display kind of busy. Also you need to uncomment a different line in the configuration file and install a graphics library in your arduino. This is all very easy to do and is referenced in the config comments though.
I kind of like the XXL display on my printer because it is pretty big and easier on my eyes