Cylinder mods = tube mods
Squarish mods = box mods
Mechanical mods = mods with NO chips whatsoever in it. Runs exclusively off the voltage of the battery, and you can't change the voltage/wattage. Has no protection whatsoever, but also no limits (resistance, length of time you fire it)
Regulated mods: mods with regulation chips in it to control either voltage or wattage. Comes with various protection such as reverse battery protection, short circuit protection etc. While it is a lot safer, it also has restrictions such as how low resistance you can go, or how long you can fire it.
You can have various permutations of mods.
RegulAted box mods, such as the vaporrshark, the atlas, hana mods, MVP v2
Mechanical box mods, such as the REO, dibby box mods
Mechanical tube mods: most mechs, such as the nemesis, stingray, glas, akuma etc
Regulated tube mods: provari, futura, zmax, vamo etc.