No, I haven't got a doctorate in szlachtology, but I have inforamlly studied this and other aspects of Polish history and culture for years. Podlasie was a place they called "laski, piaski and karaski". The latter is the cruceon (karaś -- a small fish that can survive in evaoporating, very-low-oxygen pools. They can be all head, tail and backbone covered with skin but little if any meat). Little more than potatoes grew in the sandy soil. "Boso lecz w ostrogach" (barefoot but in stirups) was also applied to the impoverished, soil-tilling gentry. Probably the percentage of szlachta in Podlasie was higher (12-15%) at different times in centuries past.
Gumishu -- I think you may find this item about the pettry gentry of Podlasie interesting.:
No-one by that (Sopneski) spelling in Poland. Someone probably changed the spelling so it wouldn't get Anglo-mangled into sop-NOO-ski. Must have originally been Sopniewski -- toponymic nickname describing somerone from the village of Sopniew or Sopniewo. Possible etymolgogy: sopel (icicle) or sopeń (dialectic for supeł -- knot); hence Icicleville or Knotbury.
What about Kuzdeba? I made a thread about that, I'm not sure if it's Polish or not, I'd assume so - most of my father's side of the family was from Poland, but they immigrated to Russia later, so I don't know if it got changed or Russofied.
KUZDEBA: Could well be Russian. There are no suitable localities in Poland as possible toponymic sources, and the only word anywhere near that in Polish is kuzdroń, a dialectic name for common ivy (a plant).
There is only 1 Kuzdeba in Poland who lives in SW Poland's Opole area.
Re:Zak. ŻAK from the Clan of Trach 1500
ŻAK: Etymology could incldue the following:
1. żak -- schoolboy, student, scholar
2. Żak -- Polish spelling of French Jacques
3. Zak -- Jewish rabbinical name from Hebrew contraction meaning "holy seed"
4. Toponymic nickname for someone from Żakowiec, Żakowo, Żakowice, Żaków, etc.
What does Szczepaniuk mean?
Eastern Polish patronymic nickname-turned-surname -- the equivalent of Stevenson.
The ethncially indigenous version would be Szczepaniak.