I am going to preface that my answers might be a mix of my own experience as a GM, player, and general roleplayer of ten years (as of June of this year). There might be variations that some have already said in thier own posts, but that's probably because a lot of us have similar views about this particular subject.
What is your opinion on character sheets?
Much like it has been stated above, I think they are a necessary evil, as well. Character Sheets, regardless what type of RP you're doing/making (1x1, Group, or Arena), they require some frame of reference. I do think that with each RPing category, they have their varying degrees of details. 1x1 character sheets can afford to be more simplistic than what you might see in group rps and Arena rps. I feel Arena specifically needs to have just about every detail in writing because you need to know the character and what to expect so your reactions aren't wrong. In groups, depending on the kind of roleplay it is, the details, while important, is more about building relationships and creating a cohesive story. Sometimes sheets need length and sometimes brevity is required, but more often than not, regardless of the RP, you will write a sheet.
Faceclaims? Real life? Anime? Digital? Hand drawn? None?
If that's your thing, then do it. If it isn't, then don't. Personally, I love images. I find giving your character some sort of visual reference also gives them an additional layer to their identity. Plus, it's certainly easier picturing the character if you have an image in mind. With that being said, I also recognize that some on the site may find them distracting. And depending on the genre you're using a character for, it could prove to be somewhat of a distraction if they are relied on too much. That's why I feel like it's best to limit yourself and don't overuse them. One or two should be enough, I find.
Color codes?
As long as you don't use eyerape blue or some other hard-to-read color, you'll see no problems from me.
What's the 'right amount' of images?
Depends on the RP and sheet.
Freeform or GM provided code?
My view on this is, if you're going to join someone's roleplay, don't be that one asshole and use your own format. It says a lot about a person if they can use the template provided. You can fancy it up however you like. I just never liked seeing how people purposely use their own template simply because "they didn't like the one provided". I'm sure, if you ask nicely, the GM may let you trim it down if they are non-essential parts of the sheet. As long as you give the information that will tell the GMs and players what your character is about, it shouldn't be a real problem.
Things that should be included/excluded?
I used to believe that including likes, dislikes, fears, hobbies, and habits belonged in a sheet, but now I find those things are left best to find out in the IC. I have nothing against those who feel these belong in the sheet. If that's your cup of tea, then I support you 100%. I'm just saying it's not my thing.
What is your character creation process?
I take inspiration from various mediums: novels, TV and film, anime, art, etc. If I have a concept, I go with my gut. If I need inspiration, I go to things that fit the character I am making. If it's a slice of life character, I will go to my favorite real life dramas, soap operas, teen dramas, etc. If we are talking fandoms, I watch/read said fandom and see what happens. It's honestly the combined total of my own interests plus whatever my brain cooks up. Sometimes the character ends up like a forced fart and sometimes it's the best thing I've ever written. Whichever the case, I am thankful the inspiration kicks in when it does.