Over 100 years ago Wilhelm Bogusławski proposed these names in "Dzieje Słowiańszczyzny północno-zachodniej do połowy XIII w.":
He is correct - those groups you mention are just some of the more than 20 groups that would've fallen under the 'Lechite' branch - modern day Slavic people that spoke similar languages and lived around Poland. Again, he's referring to 'do polowy 8 wieku' around the time of the Christianization of Poland. Mieszko I stated that he wished to unit the various Lechite groups - Lugii, Venti, Gepids, Rugii, Polans, Silesians, etc. If we're going by specific tribes and groups then yes, those would've been the people who dwelled in Poland around the 8th century. However, these tribes/small city states would've origined prior to the 8th century from a mix of Vandal/Goth/Norse/East German/Sarmatian mix - of course depending on area - the people near the Baltic like the Rugians would be more influenced by Norse/Goth than say Lugii which would've been more influenced by Vandals/Germans and possibly Sarmatians even.The Lusatians were way before this time (1000BC-500BC).The Lugii have been identified by many modern historians as the same people as the Vandals, with whom they must certainly have been strongly linked during Roman times
Also, remember that sometimes names like Lugii or Vandals can be interchanged - depending on how specific we want to get. Herwig Wolfram:"In all likelihood the Lugians and the Vandals were one cultic community that lived in the same region of the Oder in Silesia, where it was first under Celtic and then under Germanic domination."