I know you should not have NTA on the same server that your database is running on. I've run NTA on the same server that NPM runs on all the time, I guess it really boils down to how much traffic you have going to the NPM server.
By installing the NTA module on other polling engines, it would install the NTA listener where you could send flow data to other than the primary NPM server.
You should run the exe on any Orion poller to which you are planning to have devices send NetFlow data.
Yeah, that's what I figured it meant. However, the way it was worded in the release notes didn't make that very clear (at least not to me.) The release notes state that "Orion NTA should be installed and fully upgraded to this version on any and all Additional Polling Engines and Additional Web Servers you are currently using to monitor your network." It would have been more clear if it said something like "Orion NTA should be installed and fully upgraded to this version on the Primary Orion server, any and all Additional Web Servers, as well as any Additional Polling Engines which you plan to use as NetFlow listeners."
Since I don't have any plans to begin sending NetFlow data to my additional polling engine, I didn't run the installer on that server. My upgrade ran smoothly on my primary Orion server and my additional web server and I don't seem to be having any issues with the new version.