@Ardi248 You really need a strict or firm cancellation policy. We use Strict and accept we lose some peoples bookings but those we get will be more likely to be honoured. I have a theory that people book moderate and/or flexible and then they see, just before the free of charge cancellation runs out, if anything better/cheaper is available and, if it is, they swap to it.
On people numbers I disagree with @Helen3 . We have a price for our apartment that sleeps 6. It is the same price if 2, 4 or 6 people book it. Recently we had a booking for 3 people and a change request to take it to 6 which we agreed to (at no extra charge). Now if we did have a cheaper price for say 4 people and extra charges for guests 5 and 6 we would be forever worrying as to how many people were staying in the apartment and some guests would certainly try to rip us off.
I should say Helen is not wrong - every host has different ways of doing things and different criteria so we all have to Mae our own decisions.