I want to know that priority order of R2R, NOS, No Filter, Descrete for best DAC.

Sounds like knock-offs. Why on earth would anyone here want to help you?

I'd say NOS is going to be high priority (for tonality, going OS tends to grey out the sound) and having a real reconstruction filter helps with compatibility. Discrete reconstruction filter normally will beat opamp, though passive is also cool. Don't use an opamp stage beyond the passive filter though, use discretes. At $800 its hardly going to have the budget for PCM1704s, but PCM1702 is considerably cheaper and might suit.

NOS + R2R: while the cost of the components is low enough, one needs to spend endless hours matching/measuring resistors in the ladder networks, or else the sound will be degraded. One well know NOS Dac mfr. has been at it for several years without a release due to this. It is my understanding they had to build a new kind of measuring instrument and source their own quite expensive resistors. Existing entry-level SS (non-NOS) dacs are already quite good and widely available at pretty low prices. I have a nuts and bolts, non-NOS USB Dac,the Wavelength Proton, and it costs around $500. I am very happy with it.

Anyone can build a NOS R2R DAC for relatively cheap these days. Making it sound good is the expensive part!