Googler here (community engagement for Android) - I looked into the developer options question, and it's my understanding that you don't have to keep developer options enabled after you enable the advanced flow. Once you make the change on your device, it's enabled.
If you turn off developer options, then to turn off the advanced flow, you would first have to turn developer options back on.
If you turn off developer options, then to turn off the advanced flow, you would first have to turn developer options back on.