https://strive4power.fandom.com/wiki/Slave_Race_Stats_and_Abilites
That will get you started, How many races isn't really important, races are similar to the first game (in our current demo state). 32 if you count the beast and their half-beast races seperately, 23 if you count them as one race.
It's not clear yet if race will play a bigger, smaller, or similar role in the sequel, mostly it seems like copy and paste currently with minor edits. The statistic system has obviously been redesigned already in the demo, whose old caps used to the second defining feature to them outsides of flavor text/default images.
I wouldn't expect more then [the] 23 in the demo, but I can see the numbers ranging form 18-38 races in the finished game before the modding community adds any.