I have to say, unless very intolerant to benzo's at the time I have seldom had blackouts caused solely due to them, I generally drank atleast a little and usually quite a lot. In my mind to black out from benzo's alone you have to take a reasonably high dose and expect it to happen, however a blackout creeps up on you when you drink with them.
Temazepam is probably one of the easiest to black out on alone, in the past I would have to say xanax bricks have probably caused the most blackouts, not because xanax is overly likely to cause this for me compared to other benzo's but because I am generally taking bricks of xanax which are a stronger preparation than most benzo's commonly available.
I would not go so far as to call temazepam euphoric, but it definately gives me something any other benzo is yet to give me which is a real body high. All drugs give me a distinct feeling in my body and you could say each give a body high in that manner, but benzo's are one of few drugs that generally don't give me a rather enjoyable or noticeable feeling in my body.
I also don't know if it is because I haven't really used temazepam or any other hypnotic benzo's for quite some time, but a relative benzo dose of temazepam on its own seems to affect me noticeably more than diazepam and alprazolam and slightly more than bromazepam which I have fuck all experience with but have had the pleasure of playing with recently a few times. 60-80mg of temazepam has me more 'high' than 30-40mg of diazepam, which I almost wouldn't describe as a high at all on its own. Temazepam definately synergises into a more sedating high with bud too.