If I was Transported back to pirate times. Could/Would I be able to drink that type of rum or whiskey? How powerful would it be and how dangerous would it be in today's standards?
Not a historian: I'm reading that rum from that time was in the range of 95.5 proof (54.6% ABV), which is not a concentration impossible to source for yourself in these times. You could try your palate on some Everclear or Spirytus Rektyfikowany if you want to try your luck with 95%. I've had both, and they are intense and liable to cure you of any curiosity.
While the most famous variety is 190, it's available at a number of lower strengths, including as low as 120. I suspect this is to allow sales in areas that have restrictions on high proof spirits.
Your warning is still valid, even on these lower strengths. Being completely neutral, it's easy to disguise in mixed drinks.