I don't know that the rail guides you chose are any better or worse, they just are. And in your desire to limit velocity, they may provide a very small benefit to you.
Your challenge is you need a Level 2 motor that meets two criteria you've set for yourself, and those are a bit in conflict with one another. First, you want limited velocity off the rail - this means a longer burn time. Second, you want to limit altitude, for which a longer burn time is going to conflict with that.
Are you willing to share your sim file with me, as well as the motors you're considering? I might be able to offer some additional suggestions, but without a sim file, I'm shooting a bit blind.
-Kevin