When I was younger, I was drawn by the idea of being popular and well-known. The idea of being featured on Webtoons or Tapas would've definitely appealed to me.
But now, I'm older, and I realize that, personality-wise, it's not for me. I don't like too much attention drawn on me and I like to have my privacy. So I'm rather much ok with having a smaller community of fans.
Hmm, well since this assuming the fan is saying it's "fan-art" and not "this is my original work", I kinda don't care. as a kid, I used to redraw scenes from my favorite shows, and I'd definitely try to match up with the style.
But I never tried to claim that I did it all on my own. As long as no one's trying to claim my work or anything, and it's just a simple fan-art, there's no harm. 
Have a Questionnaire and Announcement update. Honestly, that's the easiest way I can think to get to all of those comments from fans. Let's be honest, sometimes, the sentiments are repeated over and over:
"I love your work!!"
"I can't wait to see what else you do!!"
And they're so lovely, really they are! But if I responded to all of them, it just feels like I'm a robot who doesn't really care, and I wouldn't want to give that impression. I'd rather do a more heartfelt overall "THANK YOU" to all of the comments as opposed to leaving "copy-paste" replies that I've seen some creators do.
But, I do make an exception to some fan comments, which leads me to answer both these next two questions in one ---
When someone makes fanart or provides comments that go in depth (questions, headcannons, theories, etc), I'm more inclined to answer those. I've already had a few people leave paragraphs on why they like my comics and what interactions they've noticed.
It's comments like those that kinda drawn me in more, and it also inspires me to make more updates pointing out those headcannons and comments and giving more content to my readers. 
Well, yes and no.
All of my fans will always be treated with respect (until they do something that's not very nice, but I've never had that problem). However, some of my fans are my closest art friends (and in turn, I'm a fan of their works as well).
They're fans, but they're also friends, so they might get closer insider looks on my content. Course, I feel it's a bit different in this case because we're artist friends, so it's kinda normal for us to share our content before others see it.
But, other than that, I don't think I'd treat my fans differently based on skills or level of support. I appreciate them all.
For me, the best kind is when people start to cosplay my characters or make wholesome quality content for them. I'm a sucker for people who make wholesome headcannons, like "XYZ loves pugs and turtles!!" It's just very cute!
I give me props! Honestly, tastes differ and I don't know the behind the scenes for every creator out there. Yeah, maybe a popular story I see doesn't appeal to me, but hey -- for all I know, that could be that creator's 5th attempt at getting out there.
They were able to find their audience and got that advantage! Sure, it might feel "unfair", but at the end of the day -- we're all at different places, and it's easier to help each other out than to let jealousy or whatever tear us down. If anything, it makes me curious on what they do for their stories, and I might check them out to see the hype. Who knows -- maybe I'll become a fan.
Eh -- I ignore them.
I can kinda tell the difference between criticism and someone being pissy that a story didn't appeal to their personal taste. First and foremost, I create for myself. If people end up coming along for the ride, that's wonderful! But the content I make is mostly for me. I take advice when and where I can and I keep it moving. People who dislike my work have their valid feelings, but it's not gonna make me stop.
Only time I'd ever consider it is if my content ever unintentionally tread along harmful lines. I do well to put up warnings and I'm very open-minded about that. As of now, I don't think I've crossed anything lines, and I like to keep it that way.
I would interchange -- but mostly spend time for other things.
As of now, I'm at a busy stage in my life. College, family, internships. I have to balance that out, and sometimes, I might have smaller time for my fans. Of course, It wouldn't be nice to leave them in the dust, especially when they support me. I might sure I can answer questions when I'm available or post bonus content. But if and when I'm busy, I let them know.
I think it's important for fans to understand that creators have lives outside of their comics. Though, I also still think a creator still has a job to at least inform their fans when they're too busy to interact. Just so people aren't waiting months - years for a voice. It's about balance.
I'm going to interact with the veteran fan first. Usually for me, my veteran fans are the ones who have the most to say about my work. They write the paragraphs and everything else.
That's not to say I wouldn't talk to that popular creator fan or that they won't have something to say other than "I love your work!!". I'd definitely welcome them to the community and hope they've enjoyed my content so far! But, I wouldn't allow their popularity to overshadow the efforts of my previous fans.
Don't work in a bubble.
I sometimes hear people say they can't work in romance or horror or whatever, and I say "bullgunt!!"
We all have something to learn from all genres, because genres can differ in styles of story-telling and interact with one another. It helps build creativity, I feel, and you're able to pick and choose parts you want to see. If you limit yourself to only tropes you see for genres, you're not going to truly understand them.
Also, don't have limited ideas on what it means to be popular.
When you look at the works that have risen to popularity, don't focus so much on the tropes they use or the dynamics.
Look at their story, their style, their previous works.
Honestly, people can get so focused being popular, they forget that popular creators had to (and still have to) work to get where they are. In order to understand what it means to be popular, you have to peer behind the scenes and understand the work effort of those creators. 