When walking side trips aren't planned or are very minor, as when I commute, I wear my road shoes and the limited walking is no problem.
When I know I will be walking a fair amount, as for a specific shopping outing, I wear my mountain shoes and they are almost like street shoes for walking.
Both are SPD, BTW, even though I don't use cleats, just old school toe clips & straps, but that's most of what's on the market these days.