Your table should be fine just using the models out of the box from Soul Wars, but wont be big enough for a full size game. As above, the standard for a full size table is 4 foot by 6 foot. That's a tall order for people to have at home, so as your armies grow you may prefer to game at a shop or club.
Bare in mind that the armies in Soul Wars favour the Stormcast. They have a somewhat significant advantage on point values (proportional to the number of models you actually have), and also these specific Stormcast have some abilities that specifically punish Nighthaunt, while the Nighthaunt dont have anything similar in return.
Basically if you're playing the Nighthaunt side and losing, dont be too disheartened! Overall as a faction, Nighthaunt are in a better place than Stormcast I would say.
The game doesnt support 3 player play especially well, at least as far as a balanced fair match. Either you should look at it as a narrative experience and not really worry about winning as much as telling a story, or have 2 vs 1, where the 2 player team has total points in units equal to the 1 player team, and take their turn simultaneously.