What is the purpose of components not fitted on the limesdr mini V2?

I’m inspired by your sdr mini v2 file to make my own card. I’d like to know why so many components are not fitted?

For example, on this screenshot, the IC16 DAC is not useful, so why add it to the schematic?

Another example, here, I don’t understand why the loopback part is so complex with many not fitted components. When is it useful to fit the components here?

If I don’t include any non-fit components in my design, will the LMS7002M chip work?

I’m guessing it’s so that if you wanted higher resolution TCXO control you could fit the 16-bit DAC instead of the 10-bit one.

Again I would suspect optionality. Given a certain board size, if there is remaining space, additional circuits are pretty much free and it’s common to design in options for things like different build variants and to provide flexibility if certain parts go end of life or long lead. Some build variants might provide improvements in some areas, with compromises in others, e.g. increasing cost or reducing performance elsewhere. Hence it’s not unusual to see various parts which are marked NF/DNI/DNP for the regular build.

Tagging @Zack in case he can clarify further.

The E7355LF component is nowhere to be found in stock anywhere. I was wondering if it was possible to do without the component by replacing it with a simple 40MHz oscillator. Without the DAC part, isn’t the LMS7002M chip supposed to work? (@Zack )