In my opinion each of the examples can be done well. If your triplet and fingering fonts are sufficiently different and properly spaced apart, they could coexist. I prefer option C myself, as I like my fingerings to be as close to the noteheads they affect as possible, rather than at the far end of the stem. My eyes go to the pitches and comprehend the rhythm in a broader / more generic sense, so putting the important number next to the notehead is more useful for me. I don’t find the brackets offensive at all; what I find odd is when there is a back and forth between them being used and not. On 8th notes that are beamed together, either use them, or don’t. I think mixing their use is a bigger issue than the numbers being on the same side. I think it ultimately falls to the engraver to make a prudent choice.
Re: the discussion of fingerings, I’d only add them if it was necessary (or didactic, as already mentioned). I only add fingerings in my editions if it is utterly difficult to parse or unintuitive (or, like the Beethoven example, I’d want a specific articulation; and even then, if the pattern is repeated, I only do it once or twice at the beginning). That way the moments that are important to pay attention to are easy to spot and the fingerings are not ignored, as they will be otherwise. I’ll also add, as a master’s degree-trained organist (performance), I find it vexing when editions are riddled with fingerings, which get in the way when I want to add my own (that are invariably different than those the editor placed there). They get in the way and make it harder to notice my own. My 2¢. Now, I’ve been known, once or twice, to put one of my favorite pieces into Dorico and add all my fingerings so it looked nice and pretty. So maybe you’re doing that too. Either way, feel free to ignore me lol.