Just to confound
The AI Prime is similar to Kessil A160 in PAR (slightly under but the new HD version should be slightly higher I’d guess) - Filipe Oliveira has used these on many scapes so I’d check his video details, maybe post the question on his FB
With this cluster matrix design, as you reduce intensity, you also significantly reduce the “spread” of the light fall
(this will occur with other LED designs as well but is less noticeable on an array) so while you’re trying not to blast the area directly under the Prime, you’re going to be increasing the shade effect at the edges
For this reason, I always run my single A160 Kessil (60 x 45 cm tank footprint) at 100% (after the “ramp”) and just decrease photoperiod when establishing the tank
eg, 30 min ramp 4-5h 100%, 30 min ramp
Then for extended viewing, I just swivel the light so it’s behind the tank (left or right corner) and only “moonlight” falls on the tank (ie light is dimmed to lowest setting)
I have minimal algae in my setups so this seems a reasonable method
If concerned, you can always just “corral” the frogbit directly beneath the Prime
If you were using 2 x AI Prime, then I’d begin with reduced intensity