This depends on your preference and your game which means that you can set the scale/ ratio of quants/meter yourself. However, keep in mind that the range of var is limited as well as its precision and the WED Map Compiler per default limits the map size to 56000 quants.
If you are creating a first person game for example you can choose to define 2 big grid boxes (that is 256 quants in total or one large cube) as the regular height of your rooms and scale the player accordingly. This has always worked fine for me so far.
In my platformer I mostly use WED blocks to create the levels and I scaled my player to 90 quants height so I can easily use the three standard blocks to create obstacles (the large cube is the maximum height that my character can reach normally).