The one overriding actuarial concern is life expectancy. It's hard to know exactly, but long lived people will do better taking the pension later.
There may be no choice if you need the money, then you have to take your pension at that time. You have to decide how much money you'd like to spend in your 60's compared to in your 80's as well. Maybe you'd just rather spend it now.
RREGOP is integrated with RRQ so it will be reduced at age 65 no matter when you take the RRQ.
If you continue to work (and earn more than $3500) while receiving RRQ, they will keep adding 0.5% of your earnings over $3500 to your next years continuing pension amount. Even if it's more than the max pension.
There is a downside to high pension amounts as the survivor pension is a combined amount with a maximum value. If you go over that amount then you lose out compared to having a smaller pension to start with.
These complex calculations need some thought unless you come from a long lived families or you need the money now.