I would never advise anyone to start at 24.
I was a 2 pad smoker and on an ego was at 18mg. 24mg was to much for me there
Some people need 24mg. When I started vaping I would have gone back to smoking my pipe had it not had that high nicotine. But then again back in those days (early 2013) sub-ohm didn't exist and top of the line was ego twist with a T-3. I did step down after two weeks, but some people actually need that high test juice. Actually I stepped down from 24mg to 21mg first and then to 18. I started manipulating juice early being that I'm a chef and I'm comfortable playing with flavoring agents and so on.
@OP
I would say that 24mg @45w is far too much nicotine. I sometimes get throat burn vaping 6mg at 25w. I'm not sure as to the science behind it but it seems the more power you hit your juice with the easier the nicotine is absorbed into your system. Also it could be any other factors. PG sensitivity, dehydration (that is a biggy right there, the first step to curing sore throats in a vapor is to drink a liter of water ime), filthy coils/wicks (I find I need to change my cotton frequently in my rdas and rtas, I can only get a nautilus or Atlantis/Triton coils to last me about a week or two, beyond that it is toast maybe three if I'm just vaping menthol), or the particular flavor you're vaping. For example I have problems with some flavors, but not others that are related.