This relation is quite complicated.
SRC = Sample Rate Conversion
Mixer requires the same sample rate from all sources and various clock sources must be perfectly synchronised, otherwise result will be garbage. It is why you have selection for a common (mixing) sample rate and bit depth. All sources are converted to the same sample rate before mixing. If you chose a rate that is not supported by your DAC, output of mixing will be subject to yet another sample rate conversion before sending it to the DAC. Here Windows is clever, as it shows only sample rates supported by your DAC,
but not always, so you must know what you are doing.
The settings in your screenshot is valid only when your player send your sound to the system mixer which is a part of Direct Sound (DS) driver stack. If your Zoom Player can use WASAPI system interface instead of DS, it can bypass mixer competely, so the above settings will be relevant only to the sound sources coming through the mixer from a system or other applications.
Read a player manual how configure WASAPI in
exclusive mode, so Windows sounds or other garbage will not get through your HiFi connected to your DAC.
if USB is sending as 44.1khz via foobar or window player, does the topping dac basically upsampling/sampling to something else ? i guess i'm not quite sure how the relation between window output sampling rate vs external dac sampling works
It is a Foobar or other player that sets the parameters for USB transfer, but only when using WASPI driver. When DS driver is selected, the settings on your sreenshot is used. Topping or other DAC accepts data stream it receives. When using WASAPI driver in exclusive mode, then any file you play is sent to the DAC in a native mode of the source without conversion. A DAC typically is able to recognise format (whether PCM or DSD) and adjusts to the sample rate and bit depth.