You are quite right.
The big change though is the amount of flash memory now needed to accommodate the big increase in firmware size driven by the so-called AI feature sets.
Much of the RAM is still assigned to buffering the video streams as opposed to processing data for the 'AI' functions.
Custom firmware - well, realistically, that would be a massive effort.
Look how long it's taken Hikvision and Dahua to make progress, even with their scale.
Exactly. The specs of the camera will say if it does AI LOL
And I would like to see someone with custom firmware do better than what Hikvision has done with all the resources they throw at it.