I only use fall and war of as back ground

the moment they go though the portal they crash on earth just as with G1, during ancient times
they all fall into a million years taking stasis before waking up in our modern times

The cons would have been on their own ship that crashed somewhere else, far enough away that both sides wont know where they are, optimus would expect them to also have crashed on this planet.
megatron would just try to get his stuff together, though megs would fear the bots awakening as well
they would likely have woken up 1 or 2 days before the bots, having a little time advanage with the planet and repairs on their side