Ah yes, this is one of my areas of expertise.
A) if the protection is bulky (e.g diaper) then my clothes become a bit tighter. If they were tight to begin with i can't wear them comfortably (or sometimes do them up)! I absolutely understand where you're coming from here. I really hate if there are sharp seams pressing against my diapers - they squash the padding and make the diaper less absorbent. Sometimes going up a size will fix it.
Sometimes, though, you actually have to find equivalent but slightly different clothing. For jeans, if I can find a size big enough that the crotch is low enough not to press into my diapers, the legs are two feet past my toes

I've mostly switched from jeans to casual pants that have a convincing denim look but are stretchy and made of something I'm not clear on - they wrap around my diaper and don't press into it. The downside is they don't shape it as much so the bulge is a little more visible.
B) i worry people can see that i'm wearing protection (my mother once declared that i should not be wearing the sort of pad she'd noticed i was. She was clearly looking for it but still)By and large I suspect it's not a common problem. I've worn some ridiculously thick diapers but as long as it's not either (a) a cloth diaper, which can be full-on globular at their worst, (b) under really tight clothing, or (c) messy (which creates a distinct lump in the back), there's a better than even chance no one will notice. Of course, people who know will 'notice', even though they might not be able to actually see it.
C) can you ever feel comfortable in lightly coloured clothes? Does the fear of leaks make you dress differently?I fear leaks less than I used to, and I'll dress in light clothes if there aren't really practical or non-incongruous options in dark colours, but yeah, I do prefer dark colours. They hide crescent leaks on the leg, but they also hide the shadows of a lumpy-shaped butt from a messy diaper.
D) bladder spasms and retention make some clothes physically uncomfortableI haven't had this experience myself, so I can't say.
E) stuff needs to be easy to get off in a rush. I also seem to wear the same easy shoes simply because i cannot face taking them off when my clothes are wet. Putting shoes on once is hard enough.I absolutely relate to this.
The way I dress now is, unfortunately, harder to get off than it was when I was continent. With continence it's just underwear and pants. When you're incontinent, diapers are hard enough to wriggle out of without messing up the fit, but I also wear plastic pants and a snapsuit over my diaper, I have a tendency to wear button up shirts (so a round neckline looks less incongruous as an undershirt), and when I'm thickly diapered I tend to wear more outerwear to obscure my outline.
The upshot of this is that when I started having messing accidents, I switched fairly quickly to just filling my diapers instead of trying to toilet. I don't have any difficulty undressing but I was wearing so much fiddly clothing that by the time I messed, I was still wearing enough clothing that I could probably just walk straight out of the cubicle. It was easier just to fill my diapers where I was than to walk all the way to the cubicle, try to get undressed, and end up filling my diapers anyway.