“Infinity Edge System” means that is at one or more sides an open edge overflow in a open surge tank, the open edge is mostly build with granit or tiling,
it is an nice design feature what looks like a bit as an waterfall to the open tank.
the water level is lower than the top of the pool .

“Skimmerbox System” is the easiest system to build, there are 1or more skimmer boxes installed
to get a top of the water suction ( as an overflow ) to the skimmer to keep water surface clean
from dust and leaves etc.
its need less space than the other systems and the water level is mostly 10 cm lower than the top.