Those details will come in time, but for now, the only person who has the Space Stone in the present time period is Thanos, as it’s in the Infinity Gauntlet along with the other Infinity Stones.
Now, whether that would result in two Space Stones being in the present or it would erase Thanos ever obtaining the Space Stone to begin with remains to be seen.
If it’s the latter, Captain Marvel would almost certainly have a leg up on Thanos, and the Mad Titan’s snap would, presumably, be unable to happen.