I can kinda relate to the part about the personality. I can perfectly picture in my head how my character will act, what their mannerisms will be, their manner of speech, and all that - but sometimes writing down their personality is difficult. Oddly enough, I don’t struggle to fill in the “personality” segment on a character sheet, but sometimes I’ll realize belatedly that I didn’t describe them well enough, and that the personality I wrote down isn’t really what I had in mind.
It’s hard to explain but yeah, it’s a problem I have now and then
The appearance is the last thing I worry about, because I never want to rely on it, in any way, shape, or form. That's not to say I downplay it as a rule, but it's usually decided late in the process, or pieces fall into place as the character is developed.
For me it's the synergy. Making a character good for a story, not just good because it's good on paper. If you know what I mean? My thing with characters is, make a character for a story, give it a purpose, and shape it so it plugs in as easily as possible.
I like synergy in character arcs and stories as a whole. Nothing worse for me than six off-brand randos crashing into each other until some chemistry forms by force. I largely got out of RP the last 4-5 years due to tiny, seemingly inescapable pet peeves piling up.
Appearance is unfortunately something I spend the majority of any CS deliberating on. Written appearances are always tedious to write knowing that it'll end up being boring to read regardless, and choosing to instead take the easy route and find an image that suits the exact archetype I have in my head at any one point often takes some digging.
Perhaps the most difficult of all is inspiration. Sometimes I'll be typing up a character and think to myself "this is gon be some good shit" only to get into an RP the next day and find myself with a much more interesting idea that I hadn't thought of that makes the character that I actually made blush in comparison. It's tough to come up with features that stay interesting, so I'll usually make sure to take inspiration from some form of media to ensure I don't lose the original spark that made the idea so appealing to me in the first place.
Personally, personality and appearance comes most easily to me. But backstories oh my god.... XD. I think my main problem is that I'll make this super over the top tragic backstory or one that doesn't really shape what kind of person they are today. I also can never name my characters for some reason.
I always make the same scenario for myself. If I were to put all of my current characters in a room and have them talk, would you be able to tell them apart just by them talking? If no, I've failed creatively.
Names, it's always the name. If I had a penny for every hour I've struggled with a name, I'd have quite a many penny. And then there's accents and how they would sound to another person. Should they have a deep intimidating voice, smooth and soft, perhaps something musical? I can never quite decide.