I share a similar sentiment with Jess where it's fun to play as a character not like yourself. You get the freedom of not limiting yourself, inserting traits and watching how they unfold and grow as a character with all the experimentation. Characters where they're heavily exaggerated I find are the easiest since there's not much internal conflict from them reacting a certain way. And if not heavily exaggerated I try to fit one major quirk into their actions.
When I started out with Charely my very first term, I essentially put more of my traits in at the time since I was closer to that age. He was talkative, polite, always up for an adventure but behaved in class. Basically a good little student.
Since then when my characters start out young I tend to revive that personality since around that age I remember it was all about having fun and being the coolest over being the best academically. I kept that trait with Charely where as he matured into adulthood he lived by the book but made a point to consider other's thoughts before his own while keeping level headed.
I think it's natural that we put a little bit of ourselves in our characters while mixing it up with people we know in real life. Wade like me was caring and willing to go so far to help his friends out, but the difference strayed with his exaggerated love for naps and pickles.
It became his little quirk where being happy is all that matters and making sure others are happy as well. What also helped was when it came to picking out models for my characters I dug into their social media to see how their personality is and try to incorporate that in the character. Since Wade's model was adventurous, loving to surf, skate, and basically did goofy antics I gave them to him as well.
For Javy as my first Professor, I did the same thing with looking into David Gandy who was always clean cut. Mixed in some Ravenclaw stereotypes where he was bookish, well-groomed, and very articulate. So he tended to creatures while wearing a suit. Writing out his posts always came out the longest compared to my other characters. He was strict with discipline but attempted to be fair. With Justin, he was a major difference from Javy. I had alot of fun with rping out his reactions to situations. I would describe him as heavily exaggerated, friendly, and a very stereotypical Slytherin. He was overconfident, outgoing and always making connections with others to better himself. He was nice but not one to cross because he has such a fiery temper.
Since he was an exaggerated character his disciplinary beliefs and actions reflected that. I think this just comes from my experiences with noteworthy teachers being very strict in general and it's easier to tie that in with Professor type characters.
When rping kids, I find it easy to have them being outgoing and looking for adventure. But as they age they focus more on their interests and working to pursue them. Also like Jess, I prefer happy endings, where if a character starts out in a bad place I have a thing with having them reach their goal for happiness in the end.