Hi,
They're going to roll off by an amount per octave so stacking them will double that amount, making a steeper roll-off curve/slope.
As to one or the other, I don't think it really matters unless they have different characteristics and one of them sounds better to you.
If you're recording, rather than streaming, I'd probably leave them both off and just use a plugin.
That's just personal preference.
I guess Im trying to see if this is normal for most studio engineers. And if not, do you prefer to roll-offf at the mic or at the mic pre.
No one can say for sure, all the responses are just guesses as it depends on these things:I am tracking using a Neumann U87 going into an Apollo, using their Neve 73 preamp. Do you recommend doing a bass-roll on both the microphone and the Neve 73? Or just one one of them? Thoughts?
You have to ask yourself if there's going to be an usable information below 100hz and if so don't high-pass going in. Otherwise ALWAYS high-pass.