IMO, Intra-Rectal Beats Intra-Nasal
I was first on Suboxone for 6 months and although I had the benefit of staying away from full mu agonists, I used it in such a way that it wasn't much better... That is, I didn't take it as scripted (16mg SL) but rather snorted 2 to 4mg tops with a day break whenever needed to keep tolerance at bay; I did this because I was ambivalent about the idea of maintenance and wanted to still catch a buzz.
After a few months off, I went to my doc and got back on after an IV coke OD

I've been on maintenance now for 8 months.
I don't get the buzz I used to get; however, taking a higher dose eliminates cravings IME (and not just for opioids
) and allows me to function- plus I still get the great anti-depressant effects
My script is 24mg but that's so that I'll have a supply when I'm off- I honestly don't know that I can ever be completely opioid-free (I was once for half a decade, but drugs change how one's brain functions

)- the purpose in having some saved is that for the few months in between my first time on Sub and this time, 2mg often kept me from completely losing it
From the start, I ALWAYS snorted my Sub, and I continued to do so this time around not to get high, but simply to save money. I gradually transitioned to snorting less and taking more sublingually... When I take it sublingually, I first brush my teeth and use Listerine, "grind" the pill against my lower front teeth using my tongue, then add a small amount of vodka under my tongue (this works better for me than the crush Sub add booze soak up with cotton ball method).
Using this method for SL, IME the BA is just as high as insufflation, the only difference being that snorting it kicks in quicker yet both ROAs last just as long (I think other posters have had the same experience). So, I've been taking 16mg/day with a BA of about 50%. (For a very short period I IV'ed it, IMO this is STUPID if on maintenance especially at the higher doses (16mg) and really messed with me re: ups and downs, etc.)
It wasn't until a few weeks ago that I decided to try plugging it. I didn't even first look up the BA as I didn't want any placebo effect: it seemed to have a high BA plus a nice rush!
Since then, I've been plugging 8mg (vs. 16mg/day) each morning after my BM. (Another advantage to plugging IME is that I'm very regular now). Not only does 8mg plugged hold me just as 16 did, but I have a "glow" to boot :D (the rush kind of faded over time to a "glow").
I crush up an 8mg pill then back-load it into a needless 3ml syringe- it dissolves very quickly that way. When I first started experimenting with plugging, I found I could get 16mg and even 24mg in 3ml of water, although I filtered it with cotton- IMO 8mg in 3ml is a good ratio as it's not thick and there's no need to filter the solution.