The 2016 model of the M1 is over stable and holds the line of release throughout its flight path and then gradually fades left, for right-handed throwers. This midrange has a flat profile that also makes it a good choice for short side arm throws.
The 400G series is the regular 400 plastic with a shot of adrenaline. It is the base 400 plastic mixed with another resin that give the plastic a slightly different feel than the base 400 series. The additive also makes the disc more durable and requires more time to break it in.