So I got an email back from Synology support after I told them the new RT2600AC doesn't have performance issue with VPN Plus server installed, so they told me: "since this seems to be working for you now, I will go ahead and close this ticket for the time being", meaning, always buy another new router even if the new app developed for your old router doesn't work well, your problem will be resolved.

The nice thing is Synology support has been very quick to respond to support requests and have been actively debugging the one issue I reported.

Synology support is terrible too

Hope Synology support can help out here.

Synology support has been useless.

Synology support has been useless.

Synology support is terrible too

In sending a request to Synology support, I was told to reset the configuration manually and then reconnect with a wired connection to redo the base configuration settings from scratch

Bought this based on the Synology support philosophy and do not regret it.

Then the 2.4G instability issues started this summer.

GUI is completely different from the old “dlink/tplink/wrt54g” static interface