You can just change the Community_Name attribute id 0x10024 on the model to the SNMPv3 community and it will work. No other configuration changes or updates need to be done. You do not even have to create an SNMPv3 profile. Just change the Community_Name attribute. The SNMPv3 profile is only needed for AutoDiscovery, Model By Ip, Model By Type and SNMPv3 trap processing.
For example, my SNMPv3 credentials are as follows:
User: AuthPrivUser
Authentication Password: authpassword
Privacy Password: privpassword
I can manually change the Community_Name attribute to the following and save without creating an SNMPv3 profile and Spectrum will start using these SNMPv3 credentials to manage the device. No other configuration changes required.
#v3/P:authpassword:privpassword/AuthPrivUser
Yes, you can use the Attribute Editor to change multiple models at the same time.
I do highly recommend creating an SNMPv3 profile with the SNMPv3 credentials for future modeling through the discovery process and for SNMPv3 trap processing.
And yes, there is a performance hit when managing devices using SNMPv3. But this is all you need to