It all depends on the person. Personally, I take 1-2mg of alp (my recreational dose is 4-6mg, low tolerance but still a HUGE dose for most,) and a few tylenol about 15 mins before I IV any moderate dose of oxycodone, and it slightly increases euphoria ( to a point, if I take more then a low dose it DOES seem to suppress euphoria) and takes away this massive headache I get whenever taking it. It's the only opiate I experience this with, but I will occasionally use 1mg alp to boost the effects of other opiates. But I know some people who swear benzos suppress all effects of opiates.
Long story short, it completely depends on the person.