There is a big difference between falling off a spaceship and walking out of the wreckage of said spaceship and an even bigger difference between jumping on to a docked spaceship and falling a moving one.
We meet Shadowheart and Lae'zel on the ship then Shadowheart immediately after the crash. Lae'zel, Gale and Asterion are all close by. Wyll we meet just outside the Tiefling Camp/Druid Grove. (Is his intervention in the fight the first the tieflings have seen him?).
Karlach is found much later and Anders the fake paladin says they have been tracking her due to crimes she has committed (murdering refugees). Anders says it is their 'third battle in as many days'. Have we been off the ship for three days? Now, the murdering refugees story and the three days of fighting are obviously lies and the group is working for Zariel but it still leaves the question of how Anders and his group catch up with Karlach.
Karlach also mentions that she is off to Baldur's Gate so getting her in Act 1 seems unlikely unless the dialogue for that part is changed.
1. We know Karlach has a tadpole, so the only difference is she got caught after she willingly boarded. Apart from that, no difference at all. She survived the same way as the other origin characters did.
2. We also know Mizora was captured and her pod isn't too far from Karlach so distance is not an issue
3. Anders was sent by Zariel, pretty much the same way the gur was sent by Cazador. They're both being actively hunted.
4. Yes, canonically at least 2 or 3 days have passed if the cut scenes appear where the companions suggest getting rest
5. The paladins were fighting gnolls as well, as stated by them multiple times and are likely including those battles
6. Zevlor knows and mentions Wyl, suggesting he has been there a while, probably a day or two if you did the old church before the druids groove
7. It is pretty much guaranteed that Karlach will join in Act 1 and that her previous dialogue was a placeholder. She's an origin character.