Bose doesn’t make a Soundtouch 300 or 500, you’re conflating the Bose HOME and SOUNDTOUCH product lines.
It looks like the Bose Soundtouch line is now dead. No more 10,20 or 30 on the website despite software updates being released recently.
The Bose Home 300/500 can not be played using the Soundtouch app and instead make use of the Bose connect app. I’m not confident at this moment that you can stream across these two product lines seamlessly.
If true, this would have the unfortunate affect of killing Bose whole home audio. There is a gap in their product line currently, where one doesn’t have a “semi-installed” speaker that can stream across an entire home.
Personally, I’d like to keep (insert monopolistic wire tap service) away from my home audio experience and the Soundtouch app does that extremely well. I can also emulate owning a custom Bose DS/freespace setup by using a 10/20/30 or the soundlink adapter. All in all, Soundtouch fans are waiting Bose; a final word here is important before I invest more money.
At the least, I can build my own speakers, amplifier and leverage the soundlink adapter