You'll be 100% fine with either combination, and will be completely lucid with both as well... But, as with all drugs (solo or combo), know your limits and use some common sense and discretion.
Benzos work great for taking the edge off Amphetamines/Methylphenidate, or helping smooth out the comedown, and some like the altered effects of the combination also. I find opiates and benzos to both have good synergy with Amphetamines specifically, but sometimes I just want the Amp itself.
Klonopin (2 to 4mg) tends to motivate me a lot (especially if I take it with 2 of those Extra Strength 5-Hour Energy shots), so I mixed it with D-Amp and it works great for motivation, but does change the feel a bit and is of course more sedating.
Hydrocodone has the same effect for me solo, and has the same additional concentration / motivation enhancing effect when mixed with Dexedrine as well.
Back when I'd take Adderall (therapeutically; I don't really care for recreational Amp usage), K-Pins or Hydrocodone were a MUST for me for the comedown. I fucking hated the adderall tweaked feel.
I'm taking Dextroamphetamine now though, and I love it, as I could take literally 4x the equivalent dose of Adderall and have ZERO tweaked feel / jitters / comedown. Plus, it feels just a lot "cleaner" overall, and I can choose what I want to focus on, whereas with the Addy, the Addy would always choose what I was focused on for the next 8 hours or so. To me, it basically seemed that whatever you were doing when the Adderall kicked in, that's what you were stuck doing until it wore off.
I remember several instances of where I took it specifcially to get a shitload of work done quickly and thoroughly, and I was playing Flash games or doing something similar waiting on the effects to start, then it would kick in and I'd be playing games for the next 8 fucking hours knowing full well I wanted to work, but couldn't no matter how hard I'd try.