As for the similar units, there may be two things you are trying to say...
1) Yes many of the units in game will be similar, as the mod contains many different Hellenistic and Celtic factions, which historically, used similar units.
2) If you are speaking about the custom battle unit selection, then yes, the Romans (as well as other factions) will be able to have barbarians. This is due to the complex nature of the EB recruitment system. See this thread on how to go about choosing armies:
https://forums.totalwar.org/vb/showthread.php?t=60256
The voices are missing, this will be eventually fixed.
The timeline is quite similar to vanilla RTW actually, as the mod begins in 272 BC as compared with vanilla's 270 BC start date. To understand the faction names in EB, just think historical accuracy. CA simply made the Gallic and Germanic tribes all into one faction. EB wishes to portray the most important tribes of Gaul and Germania and therefore we are left with the Aedui and Avernii for Gallic tribes to be included, and Sweboz as the Germanic tribe. The other tribes are presented as rebels, but still have some unique units and features available to them.
Hope that helps
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