Hello everyone, 
I have a TPLINK ARCHER AX 55 WIFI router in my workshop.
To improve the external WIFI network, I've purchased a TP-Link Omada EAP225-Outdoor / AC1200 Wireless MU-MIMO antenna.
To make installing this antenna easier, I also bought a TP-Link TL-SG1005P V2 PoE switch.

The hardware installation is as follows:
* Operator's modem in Bridge mode ;
* TPLINK ARCHER AX 55 router connected to the operator's modem;
* TL-SG1005P V2 PoE switch connected to the AX55;
* OMADA EAP225 antenna connected to the switch.

Since the ARCHER AX 55 router (Easy Mesh) and the OMADA EAP225 antenna (Omada Mesh) operate on a different mesh system and are connected by wire, I want my antenna to be configured as an access point. 
To do this, I downloaded the OMADA App and switched the installation to "STANDALONE" mode and the Access Point option.

At the end of the configuration, I see that I have 3 networks:
1.    The network of my WIFI router - WORKSHOP 
2.    The 2.4 network on my external antenna - ATELIER EXT 2.4
3.    The 5 network of my external antenna - ATELIER EXT 5

Note that all three networks use the same password. 

Question 1
I don't know much about networks and I was wondering if it was possible to obtain a single network name for all of them; a bit like in a mesh network?
Or should we let the 3 networks coexist? 
When programming the antenna, there's mention of a sub-network, but I don't understand this concept?
I'd like to get something clean, knowing that there will be 10 to 15 simultaneous clients at most.

Question 2
If I buy a second antenna and connect it to the switch, will I end up with a 2nd subnet? 

Question 3
With this type of configuration, will the devices automatically connect to the best transmitter? 

Thank you in advance for your hel