Regarding running hot.... I've never used an MP-3/6.
I used to run conservative levels until I ran a Mytek 192 ADC.
Once I realized that the Mytek could soak up a hot preamp signal, I started to run hot most of the time. My rig sounded better to me when I ran hot.
I eventually switched over to a SD USBpre2 strictly as an ADC. And it also can soak up a hot signal in my experiences. And to me, my rig sounds better when I run hot.
I don't "ride" the levels... I just try to set them as hot as I can without clipping. Occasionally, I need to turn down levels if they become too hot during a show. But once I find the "zone" with my rig's levels.. and the musicians/sound engineer don't boost their levels, I usually leave it be. I try to aim for -3db. If the sound engineer and sound system is consistent with their levels, I'm not afraid to aim closer to 0db.
If the sound pressure levels are all over the place or the dynamic range is all over the place or if I can't keep an eye on my rig's levels... then those are the times when I find it necessary to run conservative.... and it still sounds great when I run conservative and boost in post... but IMO, not as good as when it's "in-the-moment" hot.
So.. I can't speak for the MixPre-3/6... but IMO, the USBpre2 sounds better to my ears when the levels are hot.
YMMV.
edit to add: I do not use limiters.