I've not dug into any of the analysis beyond what you linked in the first post @Merckx index , maybe I need to have a look around more now. I remember that all of the individuals they looked at had pretty big upticks in hits against off-speed pitches at home, but they hadn't looked at left pitches, is that still correct?
The best data have been published by Tony Adams, an Astro fan, who recorded every single pitch that was or was not signaled by one or more bangs in home games in 2017.
http://signstealingscandal.com/
He has data for the 60/81 home games for which video was available. Some of the conclusions emerging from this are:
1) Some Astros were signaled much more than others. Particularly interesting is Jose Altuve, who won the MVP that year, and had a month or two for the ages beginning in June, when the sign stealing scheme really took off. You would think he benefitted a lot, but in fact only about 3% of the pitches he saw were associated with bangs. Other players had much higher rates, e.g., Bregman and Springer about 16%, Marwin Gonzalez 25%. We don't know why this was the case; Carlos Correa insisted that Altuve told everyone he didn't want to use the system. To make the situation more complex, even in a single game, a batter might get signaled during some plate appearances, and not others. There's been speculation that maybe the Astros were using other means to signal than banging, but no confirmation of this from the team so far.
2. The banging seemed to be associated most often with breaking or off-speed pitches. More than 90% of fastballs were not signaled, so a hitter would know with pretty high certainty when a fastball was coming. On the other hand, a lot of breaking balls were not signaled, either, and multiple bangs were used, with it's not being clear, from the data, whether the number of bangs mattered.
3. An interesting analysis at FanGraphs suggests, as i noted upthread, that the biggest benefit would probably be taking more pitches outside of the zone, IOW, walking more and striking out less.
https://blogs.fangraphs.com/the-hypothetical-value-of-an-ideal-frictionless-banging-scheme/
We don't know how much the signaling might have affected hitting, but I went through the Adams data just for one hitter, Bregman (because he was signaled a lot, and is a very good hitter, though he was't the elite hitter then that he is now), and found his contact rate was significantly higher on signaled pitches, and he put more of them in play (relative to his rates for the whole season, which would include road games). Since I was only looking at signaled ptiches,i didn't look at his contact rates on fastballs, which would probably also be available.