Wow, I thought I had a working knowledge of statistics, but this might be beyond me. I'll try to stream of conscious my way through this and see if anything useful comes out.
If I'm interpreting this correctly, what the Kelly principle is basically saying as applied to DFS is that if, after analysis of all relevant variables, our opinions ("projections") differ from the experts' (perhaps manifested as DK or FD pricing, so loosely based on avg fp per game), that should increase the bankroll that we are willing to wager. The "side information" is supposedly the statistical analysis we conduct that provides projections. In that case, it makes it sound like how much you'd wager total per day, as DK and FD pricing is provided once per day and you build your projections from that one wave of data.
Maybe another way of looking at it would be how much bankroll you want to put down on each line-up; line-ups that mirror commonly touted players ("cash" plays) would warrant smaller bets in that case, while encouraging larger GPP plays, though this is contingent on the quality of your projections as compared to others, since we aren't going against the book. That also goes against common advice here that cash games should be the priority for steady bankroll increase, while GPPs are more lottery tickets. Although, since there are different cash lines, perhaps the Kelly principle treats GPPs and cash games the same (might influence the "stated odds").
What is fundamental is the quality of your projections then, considering the importance of the quality of side information in that formula. To fully utilize this, I would suspect you'd want to look at past data from your projections or favorite projection sources and establish a correlation between projections and true output as a metric for quality, which then informs you which projections to use, and may establish how much bankroll you put down per night/line-up. Someone used to do that in the mega thread at the beginning of the season for the most popular projection sources, but those threads started getting huge, and I haven't seen them lately, sadly.
Or I am wrong about all of this, and I need to just go back to sleep.