The jacket I think might be "slightly" less warm than the Mionn. But I personally feel like buying the Mionn is better for the more unique/better design, you can get many lightweight puffer style jackets imo
I think it helps I'm the ideal height/weight for Veilance I find it's made for slender and tall people I'm 1.83/72kg or 6'0/160lb in imperial. Across all the pants I'm a 31, jackets I'm a M, Tees I'm also a M. However if you're more muscular in the legs I find it might benefit some people up 1 waist, certain items like the Conduct Anorak some people might also benefit from sizing up if they wish to layer something more than a plain t-shirt. The main complaint I have is the lack of inseam choices for pants, many of their pants are alot more smart/formal looking and would benefit greatly from that, I myself have fairly long legs so the pants don't stack but for alot of people the fit isn't too flattering. As I said earlier too if you have really buff legs you're also screwed often times.
I personally feel like buying something like a Mionn IS as a mid layer and then buying a monitor/field LT to use as shell might be more beneficial as you get two items for nearly the price of one, and it doesn't look as "bulky" Imo