I am glad that you run huge sessions on an old uncertified Windows machine. All that proves is how temperamental Pro Tools is that it will work on an old uncertified machine, but not a new certified one...
As a programmer of almost 30 years, I wholeheartedly disagree that Pro Tools does not have optimisation problems, and for the following reasons. I am running Pro Tools 12 on a Macbook Pro retina 2013 15" (2.3G i7, 500GB SSD with external USB3 drive for session data, 16GB Ram, 2GB Nvidia 750M graphics card) (an avid certified machine) and have done all of the optimisations listed here:
http://avid.force.com/pkb/articles/t.../Optimize-10-9
I have also removed all plugins that I do not require for the session from Pro Tools (but have not done so for S1 3 or LPX). If in fact the buffer works as you say it does, then why do I have the hardware buffer size option here?
https://www.dropbox.com/s/xs9o4w2zux...%20am.png?dl=0
If by default there is low latency recording and 1024 samples on playback (no wonder it always stutters with dynamic plugin processing if it's hard coded at 1024). Talk about lazy programming if you can't even set visible = false to something that is no longer relevant...
Why does a machine that works perfectly fine with a session in Logic Pro X and Studio One 3 have trouble running the exact same session on Pro Tools 12?? Obviously Logic Pro X and Studio One 3 use some voodoo magic to be able to provide a better experience with the EXACT SAME HARDWARE AND SESSION FILES/PLUGINS than Pro Tools.
I like many others am getting tired of hearing people defend AVID's terrible programming. In this day and age when we have more computing power than we should ever need, why does Pro Tools continue to require optimisation of certified machines, and then when it doesn't work people still say "it must be you" rather than admitting there is a problem with AVID's underlying code...
It's really frustrating for me as an analyst programmer of almost thirty years to see people constantly defend poor work... :/
So in black and white:
Same hardware, same files, same plugins, avid certified machine
Studio One 3 - Good
Logic Pro X - Good
Pro Tools - Buggy
I'd love to help AVID fix it, but they won't even admit there's a damn problem. While I'm at it, it's been over eighty days since I gave you money, where is my advertised Cloud Collaboration? Yup, no internal development issues at AVID, they're the BEST!
Also I am going to state that changing the buffer size on that window DOES affect performance and playback. So if AVID are stating that playback buffer is fixed at 1024, then why does that setting affect playback?? Someone is either lying or does not know how the software works.