Yes, they definitely grow at different rates. Willow's are bloody bionic. Squidge's don't grow fast at all. Willow covers a huge amount more ground on walks than Squidge does, so it's not that Squidge wears her down faster. Shadow's are quite soft so, whilst I do trim them once a week, there's very little to come off. Ginny needs hers doing because she's not very mobile but when she was having proper walks, they were similar to Shadow's.
They are almost never on tarmac, but when we have been at various times over their lives, it hasn't made any discernible difference and, anyway, if the nails are touching the asphalt, they're too long, so...
and what that might do to her long term relationship and trust with us
I think trust is more likely broken when you try to trick them. As long as you have a clear setup where she knows, "These are the conditions which mean a non-negotiable procedure is going to happen", then I think you're all good. The fact is that there are times when the dog has to go through something they'd rather not (eye drops, ear drops, injections etc) and so it's a good thing to teach them that there is a scenario where they don't get a choice. Of course, you can still build up to the procedure itself, so for example, pop the muzzle on, have your OH put an arm across her chest (or whatever) and then lift and hold her paw. You're not "asking" in the same way as you would for cooperative care and it's non-negotiable, but you can still break it down into manageable chunks to get her used to the idea that muzzle on (and whatever other environmental cues you use) means that she just has to suck it up for a few minutes.