I am confused with the "newer" ER605/7206 versus its legacy TL-R600VPN.

I've been reading the numerous websites and note that the newer ER605/7206 are SDNs - software defined networks.

What does this mean in terms of the INITIAL SETUP, ONGOING OPERATIONAL MAINTENANCE and RECONFIGURATION

implications??

Does this (SDN) mean that everything is controlled from the "cloud"?

I have also come across warnings that if you plan to use the ER605/7206, you must "make sure" all other

equipment connected to it are also "SDN compatible".  What does this mean/imply?

I am planning to install this in a foreign country with less-than-USA grade ISP reliability and do not want to be

"dependent" on the cloud.  I would like to buy the TL-R600VPN but note that Amazon only sells refurbished models

and there do not seem to be other sources.

Is the TL-R605 dead/obsolete?  Independent reviews have rated it as above excellent.

Any tips, recommendations or advice would be appreciated.

I must have a TPLINK router -- without WiFi -- as this is specific to my target environment:  with several

TPLINK A7 WiFis each acting independently as an AP (access point) in a multi-node (each node is

independent ot the others and has a TPLINK A7 in charge of WiFi only).

Many thanks for your attention and kind consideration.