how hard is it to get bids from fraternities?

So I have heard from some people that the top of the top tiers hardly give out bids to those that they didn't know before rush, but also a lot of people said that a lot of frats hand out tons of bids? Are both of these true to an extent? And how hard is it to get bids from the upper-middle and top tiers? (Including specific fraternities for example would help a lot thanks)