The NBR is connected to a PC or NAS with Minimserver through a network cable. The PC must have two network cards, one is connected to the NBR, and the other is used for mobile phone control, then buy a Lightning to RJ45 cable and connect it to one of the mobile phone and the PC The network port is limited to playing local files, and it can be accessed without connecting to the switch to reduce interference. What do you think of this method? Is it feasible?
I don’t know if NBR can directly connect to a PC with minimserver without a switch.
I don’t understand your proposition. Are you wanting to switch between local files and e.g. streaming services, internet radio etc? Where are the local files stored? How is the PC connected to the internet? Network bridge has only one network input. How do the two network cards in the PC interface with the Bridge especially as the sole PC network port in your example is dedicated to playing local files? How is the play navigated and controlled ?
Sorry but currently I just don’t get it.
Yes you can; just manually configure an IP/Subnet address into the NwB and your PC’s Ethernet port, and the two can communicate.
However, there is really no good reason to do that. Common Ethernet Switches are not so “noisy” that they will so easily affect a dCS component’s sound. They don’t.
There’s no reason to complicate your life with such convoluted Ethernet connectivity just because you imagine the Ethernet switch is “noisy” 
There are two network cards on the PC side, one of which can be used for mobile phone control, and the other is connected to the NBR without going through the switch.
I tried to turn off the wireless network and firewall of the switch and some useless functions, all of which improved the sound purity and transparency audibly. In the case of not using streaming music, I think it would be better not to use a switch.
My suggestion regarding an ‘improved’ IP switch between the NAS and the Network Bridge is the following:
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Purchase an off-the-shelf, basic 6/8 ports IP switch for about 25€. Whatever brand D-Link, etc…
However, take care its casing is made of metal, and there is a grounding post on this case. -
Purchase a reasonably good linear power supply of the proper voltage/amp rating to power this switch. It could cost 100€, maybe… The original SMPS power supply shall never be used, as usually too “noisy”.
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Connect the switch’s ground post to the Earth in your home (ie. typically a simple wire between this ground post and your mains power distribution strip Earth point). This way, lot’s of dirty perturbation inside the switch will be drained to Earth.
No complex IP switch/WiFi router in-between the NAS and the dCS N.B., please!
The above set-up will bring some level of audio improvements, despite not using an expensive audiophile-grade IP switch.
Take care.