Hello i have a gen question that might seem dumb but I have gotten mixed info as of yet...

Is it better to buy Mimosa hostilis root bark in whole pieces (chunks) or in powder form?

It seems that depends on what type of extraction you plan on doing. Pre-powdered bark can find itself suspended in your solvent doing a STB. Acolon_5 had a cute name for it that escapes me at the moment.

I prefer not to do a STB, mainly to try and clean out as much as I can with a defatting process so the STB is not going to be used.

defatting is a wasteful and outdated process for mimosa extraction, completely unnecessary IMO. Just proceed as usual without defatting (even if you do an A/B), and if you want, recrystalize the final product. That is a much more efficient way of cleaning it up