Just an FYI, there is currently a 100 turn limit on the early access games. They have said this limit will be removed next week with an update.
There are currently 4 races in the game. Sophon, Craver, Vodyani, and Lumeris.
Sophon behave the closest to what I'd consider 'normal' for a 4x. You colonize with ships, you research, you trade, etc. They're very good with tech and have an interesting ability where they gain a bonus to research inversely proportional to the number of other empires who have completed the technology. For example if nobody else has researched Tech1, they get a 50% bonus to all research applied to it. That bonus goes down as more others discover it.
Craver are locust swarms. They slowly overharvest their own planets until they are depleted of resources and the output drops significantly. They also EAT other races on the same worlds, so you eventually end up with only Craver population. They can never do any sort of diplomacy, only warfare as far as I know.
Vodyani are religious nuts who worship the Endless (background game lore). They're glowing energy beings in suits shaped like amazon space babes for some reason. They convert dust into 'essence', or harvest native populations (non Vodyani) for essence. That essence is used to build new Vodyani population (they do grow passively, but its slooow) or to build their big ark ships. They do not 'colonize' planets, they 'anchor' a massive ark ship in a system and exploit the worlds and natives that way.
The Lumeris are mercantile beings all about trade. They don't colonize, they spend money to buy an outpost which grows into a colony. No need for colony ships. Otherwise they're pretty similar to 'normal'. They get lots of income bonuses and use money instead of political power to influence minor civilizations.
The game has several new systems. For one, your empire is made up of political parties like pacifists and militarists and industrialists. The laws you can pass depend on which party is in power. You can influence this to a degree by controlling what is built. Population are swayed to one party or another depending on the situation and available facilities.
Planets can have populations of multiple races now as well, and some empires like the Lumeris get big bonuses for foreign populations.