I’m by no means an expert, but for me, what I consider important things about armor design for character writing:
How does it attach / how do you put it on or take it off? (magical girl transformation is a valid answer to the second question, but it still needs to hold onto the body somehow)
Where’s the padding / how much is there? (bare metal on bare skin is going to result in horrible chafing, burns or frostbite from temperature exposure, and at bare minimum it’s really not gonna keep ya warm out in the cold- metals are in part categorized as metals for being good thermal conductors! they get cold fast and they pass that cold along at a pretty good rate!)
Related to above, what problems is this trying to solve? (it isn’t just culture that makes a samurai’s armor look very different from a french knight’s around the same time period- armor is in a continuous relationship with both weapon and material technology!
ogres Armor has LAYERS (even aside from aforementioned padding, most medieval knights would also wear a tabard- fancy strip of cloth- over it, and sometimes mail underneath it, to get the small bendy spots some protection). Someone who’s particularly rich or preparing for a joust probably can’t even get all their armor on themselves- it might be designed in ways that confer greater protection at the expense of the assumption of helpers suiting them up. Could be cute for a weirdly romantic moment, if you want to? “hey bro help me get my cuirass on”)
I will fistfight hollywood forever on this subject: helmets. Heads are unfortunately full of Quite A Lot Of Blood, no less than five major mucus membranes that are definitely more fragile and sensitive than you think they are, and also your brain which, if stabbed, will stop the rest of you pretty good, and also can be rattled by any sort of major head impact. Yes it’s a small target. No circlets or tiaras do not meaningfully convey head protection. If you’re worried about recognizing your character, I just want to point out to you that even casual fans who’ve never picked up a comic know Spiderman on sight and it’s usually not about his face- just design a good, unique helmet and you’re golden. I will reluctantly give concession to contexts where it’s a unique character wearing mook armor but also if you don’t deliberately sow confusion or use it for comedy at least a little bit I’ll consider that a missed opportunity.