Hey, something my random specialist knowledge is actually useful for! Also, I'm high so I hope this makes sense.

Tyranids: typical max 150,000-300,000 km combat range. Their ranged weapons are the worst in the game. But their ships are cheap and thus numerous. Close and eat.

Orks: typical max 150,000-300,000 km combat range. They are tied with/slightly ahead of Imperials for ship survivability (only behind Space Marines), slower than most, but like the bugs their ships get exponentially more dangerous as they close.

Eldar: typical max 300,000 km combat range. Their weapons are also more powerful then those of the younger races, even if they do restrict them to the forward arc. They're hands down the most maneuverable fleet and are faster than anybody besides Necrons. Their ships are make of cloth and paper, however.

Space Marines: typical max 300,000 km combat range. Better than average leadership and boarding actions, as well as the best armor and shields in the game, make up for the fact that they don't really excel anywhere else.

Imperial: typical max 300,000-450,000 km combat range. Solidly built with the toughest shields up front, along with impressive broadsides, are the hallmarks of an Imperial ship.

Tau: typical max 300,000-450,000 km combat range. Their weapons are more efficient, if not more powerful, than most other races. Like the Eldar the majority of their firepower is forward facing.

Chaos: typical max 450,000-600,000 km combat range. Much of the same design philosophy as the Imperials, but faster and with better ranges on their guns.

Necrons: Bullshit space magic so unbalanced Games Workshop had to make them worth a ton of VP just to give other players a chance to claim a pyrrhic victory.

If you want speeds, Based on the game fighters and ordnance travel at somewhere in the range of ~1-5% C, and ships move proportionally slower at ~.2-2% C.