I think souls can be used up, since a shadow has no age limit while the soul is the lifespan and it would get smaller and smaller even in anormal body. If you distribut it on multiple bodies 70 years can be used up in 5 years.

Fact is also that the citicens spend soul parts every few months, while shadows can only be stolen once and as a whole.

Plus BM never layed importance on catching the souls of any of the supernovae or important containers for souls (like Oz for Moriah) even though it would be the best fighting power BM could get with the one even beating her commander. So individual abilities probably don't get transmitted by the soul. Otherwise it would be broken since you could distribute one person's abilities multiple times. It also makes sense because with shadows you are copying the current mirror image of the person while with the soul you are taking away the lifespan i.e. the future; blank parts.

He probably can't get it back for Pedro.

So I think while Brook can free the souls from a container it would be questionable how to identify the homie with Luffy's lifespan. Or it could be split up in multiple homies, maybe hundreds of homies consuming years of lifespan within a day.