Hmmm, well, in the 67-71 wish period Jerry indeed daisy chained his amps. This did a few things sonically, because he ran his amps pretty much wide open, feeding the second input into another input actually added drive and harmonics to what is normally considered to be a relatively high headroom front end and power section....translation,,, very clean and loud. Secondly, I'm not sure how much consideration was actually given in those days to proper load and impedance. There were additional 2 and 4 12 boxes under those twins on any given night. This yielded in some cases large impedance mismatches which again added to harmonics, drive and overdrive characteristics of his sound at that time, might have been purposeful but more likely happy accident at first. Somewhere 71-72 the tube Mac's came into play with ( at least one ) Twin pre amped out.
By mid 73 ( Wall of Sound time ) gone were the Fender power sections and the Twins were used as pre amps only feeding tube, then solid state Mac's.
Curiously the speaker mismatch element survived, thrived and was utilized purposefully in Jerry's late 70's to 90's rigs with solid state McIntosh amps run at 2 ohms, something that again added harmonic complexity and tinkle ( almost like a gritty ghosting ) to all of Jerry's clean and distorted tones.
BTW, Brad Sarno hipped me to many of the McIntosh impedance variances that Jerry used, thanks Brad!
I play in the band Box Of Rain which is all about Good Ol' Grateful Dead 68-74.
In this video I'm running my rig ( two Blackface heads, Showman and Bandmaster, one Dripn Edge Bandmaster Reverb feeding 4/ D120's ) daisy chained ala 1971 with said speaker impedance mismatch.
Hope that this helps!