The clipping you experienced in my test mp3 files when using exclusive mode is a proof that there is a conversion stage from floating point to integer before audio data entering the DAC chip.
I think your DAC comes with a driver with ASIO support. Open RMAA, click the ASIO button to check the bit format.
View attachment 111244
Int32LSB means the driver uses integer. I've seen some virtual ASIO drivers use float though. However, driver is still at software layer, RMAA cannot show what happens later on. For example, if you are outputting to SPDIF, then the format must be capped to 24-bit later on.