Hi LeKrak
I don't know for sure but I think so.
You see Tidal HiFi is the only available option for devices that can't unfold MQA audio. So Tidal will only allow upto 16bit 44.1k playback from devices that cant decode and unfold the MQA.
If you have an MQA capable streamer or USB DAC it would be easy enough to find out for sure, but as I dont have anything that can decode MQA I cant tell you for sure.
BubbleUPnP cant unfold the MQA and doesnt have the Master Audio option so it's limited to the 16bit 44.1k stream from Tidal and should be passing that through untouched.
What I can say is that it should sound the same regardless of whether it goes via DLNA or via USB to the Oppo because it's not being transcoded.
Bits are bits and as long as they dont get changed, for all intent purposes they should sound the same. (though you may need to allow for differences in the USB or network decoding and filters used within the Oppo)
I can also tell you that BubbleUPnP does indeed pass-through other streams from my local server without touching them - they come through as 44/16 96/24, 192/24 and DFF and DSF files just fine to my MC zone with a DAC attached.
You can enable transcoding on the tablet in BubbleUPnP, but I have it turned off as JRiver MC can decode anything I send to my DAC on the JRiver DLNA zone.
BubbleUPnP doesnt pass the stream directly off to MC like chromecast and spotify casting technologies do, you are actually receiving the Tidal stream though BubbleUPnP as a proxy and it's then forwarding to your DLNA device. BubbleUPnP sends the stream untouched as long as you have the FFmpeg audio decoding option in BubbleUPnP set to "Never Use" on the DLNA renderer device you're using.
You can find that setting under BubbleUPnP settings> Individual UPnP/DLNA renderers settings > Select Renderer > FFmpeg audio decoding > Check the Never use check box. Here you can also set gapless control to on if your device supports it.
So the short version - yes you're getting the best possible sound you can get for a non-MQA capable DAC or streaming device.
(well with one small exception - If you dont have an MQA DAC, the Tidal App on PC can partially unfold the MQA stream on albums where Master Audio is available and pass upto 96/24 to your DAC directly - however most albums on Tidal are 16bit 44.1k anyway)
And your welcome, you're not abusing anything, that's why we are here to help one another!