I have two setups in different countries. I want to use different SSID's. Can I access them from the same app. Or can I setup a different login? Options?

I am hoping to connect a Deco M5 AC1300 WiFi mesh system (not purchased yet) to my TP-ER6120 using only the DHCP from the 6120. I am hoping to keep all devices under the same Sub Net Mask. Will the...