Wide scan shows npc, nm, elementals, and mobs. Npc are marke with green dots, while mobs are red; nm aren't in special colors either nor do they necessary appear top of the list. The list is downloaded from server, which means you got an advantage if you are in jpn close by the servers. The scan is a snapshot, which means it doesn't auto-refresh. You can track your mob by selecting off the list, which shows up a crosshair on your map and a green arrow on you compass when you get out of the map. Wide scan is not same as your other markers, they are dots, so no worries about running out of markers, just extra precious download time. You get wider scan if your rng is at higher lvls so it's recommended that you lvl your rng, but not too much unless you are in jpn.