Is slippage modelled?

No. A limit fills wherever the tape reached it, with nothing in front of it.

There is no order queue and no slippage. Your limit fills the moment a bar touches its price, as though you were first in line, and a stop fills at its trigger rather than wherever the market was when it got there.

With commission modelled, this is the last place the simulator is kinder than a broker. In a fast market it is a meaningful difference, and it flatters entries into news and into the open more than anything else.