If I could suggest some?..
Kiev should probably produce grain as the rest of the region I hardly could recall when it was major iron producing center.
Lwow is better to produce Salt: Lacko, Stara Sol, Drohobycz, Stebnik, Stryj, Bolechow, Dolina major mines which were working since the medieval times.
Krakow (Malopolska) is also should produce Salt (famous Wieliczka and Bochnia since the Medieval) or clothes (the city and towns in the region).
In fact in MyMap Opole (Oppeln) produces mineral (famous mineral mines in the region).
Sieradz and Cujavia regions are famous for the grain production oriented on import. I really do not know any major salt mines in Cujavia to replace the grain for which it was famous in the 16th century.
Pomerelia should produce grain IMO. Much more sense really (much as Sieradz and Cujavia).
Warmia is better to produce cloth (Malbork and Elbing textile centers since the 15th century). The grain from Warmia region was not really valuable commodity.
Warsaw is better to produce cloth too. In fact it became important textiles producer only from the 16th century, but as soon as you cannot change resources in EUII, it is better to allow it to start with it (as there are already too many grains provinces).
Sandomierz region was the most important iron-specialized (hutnictwo) region of the Crown. It surely should produce this commodity.
Polostk should produce NAVS. It never produced any kinds of marketable metal (it is mistake from vanilla). Same story with Chernigov (better grain).
Regarding base taxes and manpower, if it could be possible I would make Troki 6 base tax, Volynia 4 base tax and 3 manpower, Minsk 5 base tax, Polotsk 3 manpower, Smolensk 4 manpower, Pereyaslavl 4 base tax. So, there are 8 base tax and 5 manpower to use in more populated western regions: raise Navahradak to 7 base tax and 5 manpower, and Polesia to 6 and 5 manpower.