I'm kind of a newbie too but would break down the question a little finer based on vape used. I find the MFLB to result in a tiny, slightly more noticeable smell than the Solo both in use and breath. The difference is minuscule and unless I was deliberately setting out to discern a difference I would never notice. Maybe it's because the MFLB relies on conduction and the Solo on convection. The ABV from my MFLB contains more black than the ABV from the Solo so a hint of combustion? Could also be because I've had the MFLB longer and haven't cleaned it as thoroughly as I could. When home we mostly keep to the master bath for our sessions and a few minutes after a session I can walk back into the master bath and can't tell anything went on regardless of using either vape and we don't mask the odor because, to us, there isn't any.
Another factor is how far into the fill you go - I can get between two to four sessions from a recently filled MFLB or Solo and when I get to the last session and it 'smells / tastes like popcorn' its more noticeable than the first session. BUT it's not an MJ smell.
From a strictly breath point of view - When we first started vaping with the MFLB my wife and I breathed into each other's face to see how much smell there was. Since neither of us really knew what vape smelled like our reaction was it sure don't smell like duh herb to me
My kids (early and late 20's) finally caught me wreaking from combustion over a year ago and take great joy in fucking with me about MJ since they can't believe how long I've been using without them knowing. Since switching over to vaping they haven't been able to tell simply by smell. We're one of those families that hugs and kisses on the cheek to say hello and goodbye and on more than one occasion the hello or goodbye was minutes after a session
