I think there are gems and duds with each flavor manufacturer, and yes some are more concentrated and so forth, one can use less flavoring % with higher concentrated flavorings. If you want to try these cereals, you could order "smalls", just to try, then you're not out much if you don't like them. Some flavors require a higher mix %, but taste is up to the mixer, what they want and what equipment, pg/vg ratios used...joy of diy, allows much more individualization. I use a variety of flavor brands honestly, and still have more to try.
Even amongst tfa flavors, some are more concentrated/intense... raisin and that caramel cappuccino come to mind...strong stuff here...research, trial and error
Not sure who all mbv is using flavoring wise, I know he says it's not all fw anymore even though that had been the long standing notion/rumor before..no idea what %'s used in recipes there, no idea if that 40% would be for his mixes with flavor shots added or not, sounds high imo only for a single flavoring any brand, and I never heard they mix that high before honestly