Yes, to the bass problem, yes to the volume cap. Um I'm honestly not sure about the warning, I don't remember getting it using a dongle but I can't guarantee it doesn't show up. The other 2 problems are bypassed though
Your dongle will provide the power and it's dac will provide the sound. You can't use sony sound effects but if the app has sound settings you can use that through the app- like hiby, uapp, Amazon music.
Some have bit perfect modes like Sony app, hiby app, and uaap. Amazon runs through the Android block, so you can set it to hi res streaming or not. I think it's 96 kHz or 192 I'm not sure. My dongle show 96 kHz on the hiby app when not in exclusive mode. It sounds a little livelier than usb mode to me.
But yes it makes a nice little transport. I think my first unit had both problems. Cap AND low bass and it sounded great through my dc03 pro btw if you want to upgrade I'm selling my dco3 for 45 shipped, like new- haven't even opened the accessory compartment. Pm if interested, only ship to US
Just thought I'd through that out there, it's one of the better dongles I've heard. Super clean, sips juice, runs cool.
Hiby fc6- uses a lot of juice, runs very warm, but analog sound.