I am a fan of this combination, but only up to a certain extent. My advice for this combination is to use a higher dose of dmt and 1/4 of a canister of nitrous (much more cost efficient too).
Be sure to supplement with b12 following nitrous consumption as it
depletes b12 and can cause peripheral neuropathy, fatigue, anemia as well as causing bone marrow changes and impaired synthesis of DNA(yes ,people have been
hospitalized for nitrous abuse, degeneration in the spine). Also make sure you are deep breathing regularly between whippits (hence why dentists always use oxygen in combination with nitrous oxide).
It is a "dissociative" and while it does change the quality of the visuals for me, it seems to add another element to the trip. I have had times where horizontal felt vertical and I couldn't tell which way was up (sounds horrible, i know. but I was laying on the grass in a field and it was nice). Most of the time though, at lower DMT dosages, it ramps the experience of the DMT up 2-3x the dosage. IE, on a barely perceptible dose of DMT, suddenly after nitrous I will see CEV.
Nitrous oxide can make the trip very chaotic, and after it wears off it can reduce the dmt or mushroom trip down past half the level of intensity as it was before inhaling the nitrous. I have even read of people using it to mellow out the trip on here. But, a friend has also told me it reduced their trip to almost nothing, but on another occasion made it more intense.
I have only ever done DMT first before nitrous. It never made much sense to me as DMT takes a bit longer to come on than nitrous, by the time it fully kicks in the nitrous would be leaving your system.