I suppose we are all different - but when I pick up a person strongly like that they tend to be rather personality disordered, sometimes sociopathic, or just generally unpleasant emotionally disordered people. I have concluded this is due to the sensitivity of my receivers/antennas and also due to my personal history growing up with such types. I also pick up on people who use drugs very strongly, just in passing, at the supermarket, etc. It's not very nice.
I would very much doubt the person is another empath. There really aren't that many of us, and I for one do not live in a world where 'powerful empaths' impress upon or do battle with other empaths, although this sort of thing is very popular online. (This is all just my opinion, of course.) Needy and manipulative people, people with a degree of pyschic ability, psychic vampires (even rarer than empaths, but I've met a few), all can do what this man seemed to be doing to you.
A person with strong will and a sexual desire for you, or a desire to dominate and 'be better than' you, someone who envies and resents you, can do all this without consciously intending to have an effect, simply by bringing you intently to mind.
Beware of such types! Half of what my empath thing has given me, if not more than half, is an awareness of who to steer clear of.
"So my question is: Are there people that simply have stronger vibes and externalize their thoughts and feelings with greater amplitude or something and/or is it possible that I may be more sensitive to certain specific people due to a connection or something like that?"
Yes. Both. I don't think there needs to be a connection. Someone of stong will or strong force in their personality, can forge a connection like that by the intensity of their emotional body. You may be more sensitive to someone like that because of your personal history.
"I felt him so strongly that I eventually realized that I was even feeling his physical state (e.g. agitated and mind loopy on a morning after a night of doing drugs, later calmed down after having a smoke - I neither took drugs the night before or smoke cigarettes)."
Welcome to my world! I spend most weeks dealing with this sort of thing at some point, to one degree or another - and I can assure you I am not surrounded by empaths!