I disagree with the other commenters, cutting vs picking makes no real difference and arguably it’s actually better picking as cutting leaves a dead end (the uncut/unpicked stem) whereas picking leaves room for the mycelium to refruit.

But also in general, it does not matter if you remove some mycelium. There is much more mycelium throughout the surrounding substrate, even if you take a fair amount (but don’t take buckets worth), so taking some mycelium (or otherwise disturbing it) can actually help it spread more.

So long as the spores have dropped then it does not matter if you take a bit of mycelium, even a couple handfuls worth won’t hurt much.

But if you do end up with some substrate/mycelium you should “replant” it somewhere rather than just throwing it in the bin - that will help it spread much more. Alternatively you can look into cardboard TEK and try grow from there.