I think it depends on what you want to memorize. Of course if I want to memorize numbers, I won’t have a palace where my people of the Dominic System are in a fixed position because I would probably confuse something (especially when trying to go fast). That might not apply to everyone, because I use memory palaces mainly to memorize the law. So I need to know the numbers of the §§ or Articles as well as the information that they contain. So I have the advantage there that the people from my Dominic Sytem instantly give me the §§/Articles and they interact with the additional information I want to have there.
I have a specific palace with 100 loci where I only store my people/actions/objects, but I don’t use that palace for anything else. It’s just some kind of “backup” just in case I’d forget one of my people etc.
I’ve heard that some people do use a locus with a fixed person in it to memorize words. So the person would interact with the things you’d like to memorize. I personally would use different people than the ones in my Dominic System. I’ll try to make some new journeys for words on Memory League and put 25 completely new people in them (I always memorize 2 words in one locus). The people will probably be some people from tv series. For example I have Mr. T (B.A. Baracus from the A-Team) as my number 21 in the Dominic System. But I have not used the other characters from the A-Team, so I have at least 4 or 5 more people to use there without the risk of confusion. I think the people could really be an advantage to memorize words and other things.
For images on Memory League I don’t need people to be in the loci, though. I let 2 pictures interact with eachother to make them more memorable. The first is more active or just on top, the second passive or below, so I don’t switch the 2 that are in the same locus. So if the first picture is a dog and the second is a boat: I picture the dog lying on top of the boat. If it were the other way around: The boat crashes into the dog. With that technique I usually manage to memorize the 30 images in around 15-17 seconds.
In conclusion: Yes, people make things more memorable for me, too.