First, I want to second what CoalMinerRetired said: as far as I understand, Obi doesn't store any provider passwords on their servers. If you set up your adapter through the portal, Obitalk server pushes the settings to the device, but doesn't keep the password. There is certainly no reason for them to keep it... it is your device that registers with the provider (Google or SIP), and Obitalk is not a participant in this transaction.
Now, I am not affiliated with Obihai, so I can't know for sure. It is possible that for some weird or malicious reason Obi captures the password as it pushes it to your device and then stores it in some way. If that is a concern, I would not use Obitalk Web portal at all and administer the device through device UI. There are many good arguments to do that way anyway (note, I prefer to administer through the portal - but I respect those arguments nevertheless). See
the sticky in this forum for more info.
Separating gmail accounts should be done for different reasons (there may be problems if you are reading your gmail mail, and your obi is registered to google voice at the same time). And encrypting password as it travels from your browser to portal servers and from the portal to your device is really independent of your question.