In my experience, alternate nostril breathing and spinal breathing pranayama are both very powerful. But I am not sure, if there is any big difference what you do, if it is just 5 minutes anyway. In that case, sticking with one would make the whole more simple and spinal breathing pranayama perhaps has the edge in the long term.
Although I know that this is not the approach in AYP, kriya yogis do their spinal breathing pranayama hours per day with intense effects. Also hatha yogis do hours of alternate nostril breathing also with intense efects. I did both in seperate times too and also can verify that 2 months of long breathing sessions did infinitely more to my opening than regular 30 min combined sessions twice a day over half a year or a year.
The problem is, to have high focus on breathing, you need to change your living style very fast to not burn. That means eating light, having lots of physical activity etc. The awakening speed is dramatic. 5min of pranayama and 20 min of DM is much more stable, the changes are more subtle and slow, easy to get used to them and is more safe in the long term to reach higher states of awareness.
In your place, I would try it out. Especially if those 2 minutes of dynamic chin pump are doing a big deal if there is just 5 min of pranayma beforehand. Perhaps 7 minutes SBP would have the greatest effect.