In large circuits the lower level power bussing is probably
overstrapped and the current dropped down from higher,
thicker, wider metal. In bottom-up design, if you don't
know the strategy you should at least understand the
limitations to what you -do- control, and assert the
needs that will address those (e.g. your reliability
current density limited distance between feed-points,
your signal integrity noise margin limited distance
(Ipeak*Rbus making a voltage perturbation locally
that must not take you past VILmax / VIHmin as
rated) and so on)). If you can't control it, at least
document that it's Somebody Else's Problem and
help them do their part.
Simple rule is "mobetta" but there are always other
interests.