The features they share in common are: a decrease in box resonance frequency, a boost in sensitivity and efficiency that starts in the mid band and grows with increasing frequency up to a strong peak somewhere in the upper end of the response. There is a corresponding impedance peak here as well. I believe excursion is also reduced somewhat over most of the range. Unfortunately, the location of the first peak from the slot load varied substantially depending on what modelling approach was used. The model with the throat chamber had a much smoother top-end as well. However, regardless of the modelling approach, I did not find a slot-load cabinet design with suitable dimensions whose first peak fell below 100 Hz. Enhancement of output in the 20-40 Hz range was pretty poor, IIRC hitting +3 dB at 40 Hz in the best case. I suspect my problem here is simply one of geometry. I don't know horn theory too well yet, but I imagine I need either a longer slot length or greater exit area than I can accommodate without giving up valuable internal volume.
From memory of my reading on PPSL, the decrease in resonant frequency (of the drivers - and therefore the box?) and the increase/peak towards the top end of the band/range are both features seen in PPSL boxes.
Again IIRC, the depth of the slot is the biggest influence on the response range - the bandpass effect of the slot means that only the longer wavelengths escape, so I think that a deeper slot reduces where the peak in response falls, if I have the slightest clue what I'm talking about (which is not guaranteed... lol). I'm not sure if a deeper slot reduces the resonant frequency or not, though?
WRT to the thoughts about differences in slot width/geometry due to the exact excursion of the drivers at any given time, is it really an issue? (Not a rhetorical/sarcastic question because I honestly don't know!) As I sit here and ponder on it now, surely any horn-type arrangement will have differing geometry at any given driver excursion? i.e. a driver at rest will have, say 2" from the cone edge to the face of the internal wall opposite, which will increase and decrease as the driver moves back and forth in its range? giving a differing pressure experienced in the area between the cone and the wall as the driver moves back and forth?
I'm not really sure where I'm going with this train of thought TBH... lol