Yes the VPN overhead is definitely a possible reason for buffering.
The Tablo Connect feature aka remote viewing doesn’t use VPN.
Also with the Tablo Connect feature there is a Remote Streaming Quality (RSQ) feature, was your set to something less than Full Quality? Read this about the RSQ setting:
Yep i tryed at 3mbps with the same lagging result…
So best bet is what i think that the vpn connection need a part of the stream bandwith for the communication resulting in a lot of buffering. In the other hand i dont know how the paid remote access feature work but it dont give buffering like it happen when using vpn!
So the Remote Streaming Quality feature doesn’t come in to play if you’re connected via a VPN because the phone thinks it’s connected locally to the Tablo, not remotely.
So the Recording Quality and Remote Streaming Quality are two different things.
Also if you change the Recording Quality to 720p 3 Mbps, this does not apply to previous recordings. If only applies to new recordings going forward. Did you change the Recording Quality and try a new recording?