There are always exceptions to the rule.
I do it like this
If its a dead end item and its a single item, whatever goes it does not matter.
If its a dead end item with many parts, components for each part done roughly to rule as it does not matter to much.
If its a single item that will be used again, do it to rule as its important.
If it has many parts, components and done to rule.
If it has parts that need reused in the same model or other models down the line
1) will any be change as single objects.
Yes = do it as a copy paste new
No = do it as a past or past new depending on how you bring it back in and break link at the end.
2) see No
I do it like that at the planning stage unless it's off a drawing then I know allread what needs to be done.
If I am not sure I do a test model and work out what to do that way then do the real mode to what's needed.
One exception I use, if still not sure do a save as a break links in the new version so you have both. then when you know delete one or the other.
I have some models that have linked parts in them simply because what it gets attached to does not change and I am not the person who does the change so I have to leave it linked, the person who does the change is in the US, this is where linked components and the cloud are banngers.