Do the DAC chips basically output balanced and the dac manufacturer has to use I/V conversion to make it single ended?
Sort of.
A DAC chip has a differential current output, that is, two pins. The difference of the two currents is the intended output signal. Ideally, the sum of the two currents would give net zero but in practice they don't and that signal is the common-mode signal and that must be cancelled out to reach the full specs of the DAC chip because it carries more distortion.
Normally (and that's the case here) each of these output currents is converted to a voltage with an I/V-stage, so two I/V's. That already provides a balanced output and that's what Topping uses in the D10B (with a passive post-filter). The receiver (amp or whatever) then does the conversion to single-ended to remove the common-mode signal.
For a dedicated single-ended output at the DAC output there must be a subtractor stage in the DAC after the I/V's that extracts the difference signal and also often does additional high-frequency filtering. This is what we have on most other DACs which have SE outputs (like the D10s). Sometimes further circuitry is added to also create a signal-balanced output.
There are other ways like combining the I/V's and subtractor and filter and unbalanced+balanced outputs in one single circuit block around one single fully-differential OpAmp or one standard dual OpAmp and that's what I'm going to design (soon, hopefully).