I have experienced this and I believe it is due to the catecholamines. I agree that I feel lighter and more energetic. I’m not sure I agree with feeling stronger, atleast not top-end strength. As in, I wouldn’t try to max or do 3RM on a fasted workout because I can feel the difference in power. But I thoroughly enjoy lifting in the 8-12 rep range and I feel great. As you mentioned, fed workouts can feel sluggish. But I believe that “fed” has a lot of levels. As example, I ate a few mozzarella strings a few hours ago. I’m not fasted, but if I worked out now I wouldn’t feel sluggish at all. After I have lunch in a bit… I absolutely cannot lift comfortably until tonight.