Are Imr 18650 batteries safer than other types even if some are unprotected
Yes, they are quite safe.
Not as good as NiMH cells, but better than lithium-ion pouch cells, due to their different shape(cylindrical), and how the internal components are arranged.
Almost all cells these days are not really IMR. This will help you hopefully and if not, he has a lot of other videos and knows his cells.
Yes, UNprotected IMR are safer than UNprotected ICR, IF you use them in a light that has NO Overdischarge protection built into the light. BUT, it is up to the operator to prevent OverDischarge if neither the light, nor the Cell, have OverDischarge protection.
No, IF you OverDischarge UNprotected IMR in a light that has NO Overdischarge Protection built into the light, instead of using a Protected ICR in a light with NO Overdischarge Protection built into the light.
DOES the light you want to use HAVE Overdischarge Protection built into the light? If YES, you are fine with UNProtected cells.
If NOT,
Are you feeling lucky?
What cells are you using that are really IMR?