The Li-po and Li-Mn are different chemistry, the Li-po will vent much more violently than a Li-Mn might. Both are reasonably safe when used properly.
Li-Po is just another construction for the layers on the batteries. It could be Li-Co, Li-Mn and others underneath, it refers mostly to the insulator electrode films between anode and cathode, which is different than standard 18XXX cylindrical, but the anode-cathode couple remains.
What is more, almost every mobile and tablet in the planet now runs on Li-Po planar, with batteries more or less rectangle-shaped, but with Li-Co chemistry, because it provides the biggest capacity even though with much less current available. I bet that our vaping devices with Li-Po really are also Li-Mn, like RC batteries, just in Li-Po fashion because now theyre starting to get competitive manufacture prices and they are suitable for the final application.
The thing about Li-Po is really two things:
* They swell under certain circumstances, as they lack of a rigid container and under heavy loads (charging or discharging) there is some gas build-up, transitory, and it cannot be just vented. They battery might be OK, so the manufacturer of the device should provide enough internal space to let the battery swell up without risking neither the appliance or the battery: this might ruin any size advantage for Li-Po geometry, also taking into consideration capacities (like it happens on the Hana vs. Hana mini mod). Our iSticks have a foam container for the 'R18650D' Li-Po precisely for this reason.
* They cannot get punctured, cut or just pressed in any way: they are really fragile compared to normal cylindrical lithium, they depend on the container to provide a secure environment for them.......(charging currents, discharging currents, voltages granted in use and physical stability). In our iSticks, that 'safe environment' is provided by the chipset (for currents and voltages) and the aluminium-extruded case, which is really sturdy.
Other than those, they are not a piece of C4-dynamite, you know!