Speed and arrow drop will depend upon the draw weight and the arrow weight. So, a 45# bow can shoot the same speed and arrow drop as a 50# bow, given that the arrows are set up properly (that is, if this would be part of one's goals).
So, I wouldn't concern myself with that question.
As far as the ability to kill game, listen to Ted Nugent. He says his petit wife shoots, I believe, 38#. She has had no limitations in the type of game she can kill so far (I don't think she has tried Cape Buffalo with 38# but she has taken Zebra and a whole bunch of North American game). Therefore, your 45# bow is only limited by game laws in various states.
Personally, I think that, if you have an itch to try something different, you'll never be happy until you do. And, don't frown if it seemingly doesn't work out because even then you will have learned something valuable for yourself.
I've been shooting a 50# bow, which I finally tested out and found it to be 58# at my draw length. I love shooting it. But, I bought a 36# bow to give myself a little different perspective. And, it has. And, I've been learning about myself, and taking that back to my other bow. The 58# bow is certainly enough for moose in Ontario, which I may well do. In the meantime, I have a beautiful Blacktail on order - 48# at my draw lenght. My only regret about that bow is that I won't be able to hunt Elk in Oregon or any big game in Ontario.
Enjoy!