For the priority question: set.priority(4) should make it so that ego will not be drawn behind another view. But it may be possible for ego to walk over that view. It depends on what specifically you're trying to do.
For the speed, you need to set the variable cycle_delay. It is possible to change this in the middle of a logic, I believe, but it would be a good idea to save the player's old speed settings in a variable, so that the settings can be restored when the player leaves the room. You would do it something like this:
#define old_cycle_delay v200
if (new_room)
{
// whatever code is in your new room section
old_cycle_delay = cycle_delay;
// this is the fast speed setting
cycle_delay = 1;
}
// anywhere that the player is sent to a new room
cycle_delay = old_cycle delay;
new.room(...);