@RouterHang 

You can't use two routers to build a OneMesh network - Q10/A10.

What you can do is to set the C80 in AP mode (Case 1), connected by wire to the main router (AX10) and extend your wireless coverage across your home.

That's your 1-st scenario.

Your 2-nd scenario is redundant since C80 supports Operation Mode - AP mode natively (it's the same thing).

In both cases your internet source is AX10 through its wired connection to the C80 AP and then by wired cable to your PC.

@terziyski

i mean ,when i enabled both AX10 and C80 mesh system

where is the internet source come from ? question 1 and 2

@RouterHang 

Re-read my previous post carefully. The blue text is a hyperlink which leads to a particular resource.

It doesn't matter if you have enabled OneMesh on AX10 and C80 - they can't build a mesh network.

Your internet source in both cases is wired connection of you PC, not a mesh network.

@terziyski 

i still confused

you mean , if i want extended my network using mesh system

there is only 2 way, using range extender or power line adapter ?

its that you mean ? so in mesh system, only 1 router allowed ?

@RouterHang 

That's correct. This is by TP-Link's design for OneMesh.

@terziyski 

oh my god , this is getting worse than i expected

because RE/PLC have poor hardware spesification , RAM and processor

i expected can build mesh with 2 router, although without wired cable,  so there is no wasted device

because other brand can make mesh system with 2 router also support wired cable

now lets say about deco

if i change my C80 with 2 deco and using mesh with wired cable

example

AX10----Deco1----deco2

when i put wired cable from AX10 LAN1 to Deco1(WAN)

and Deco1(LAN) to Deco2(WAN)

and Deco2(LAN) to my computer

with thats example condition , my computer/phone internet source is from wired cable and mesh system still working?

so it is that the best design for getting maximum performance or bandwidth also lowest latency ??

@RouterHang 

Yes, you could do that - here's an example for Deco ethernet backhaul.

In this case you'll have a mesh network and seamless roaming.

@terziyski 

last question

can i mixed both diffrent type deco ?

example 2 Deco E4 and 2 Deco M2 in same mesh network?

@RouterHang 

Yes, this has been described in the following Deco FAQ.