Sounds are limited to nothing with BlueRail unless you add a DCC board. Then you're getting into real money for O-gauge currents. Just the BlueRail board is $150, then you need a DCC decoder that will handle full sized O-gauge tasks. Finally, you still have to add the DCC compatible sound board.
I think I can wait on this option until the costs get more in line.
You just need the Bluerail board and a sound decoder. A third component is not necessary.
I would not take one of my well working engines and transition to BR, but I would take engines with fried boards or even buy conventional engines I liked to upgrade.
My AC BR board was $145 and I purchased a Soundtrax TSU 2200 for less than $100. So an upgrade is similar to other avenues.
Also consider... A Soundtrax decoder has many many options for sounds and lights that I can change and customize on the fly. No need to hook my engine up to a computer and download a different sound set which is still not customizable.
I can also run my engine on ANY layout. Legacy, DCS, conventional. I just need 13 volts or so.
Oh and if I switch out two wires, I'm running Deadrail.
I will post some new video when I get the Atlas AEM-7 running with sound. You are very familiar with the DCS challenges with that engine.
Maybe it's not for everyone... But it's another option for some.