He said "RAM preview" meaning he just made the RAM preview so you could preview it. In newer versions there isn't a need for that.
My SPACE BAR does not do Play/Stop function properly. That means rarely it works and most of the time it will not work. Therefore I am looking for a aleternative method. Detail here
How does it not function properly? What's the issue? You can change the shortcut key to something else in the Preview panel and it's more like a RAM preview in that way, but I don't think RAM previews don't exist anymore.
"How does it not function properly? What's the issue?"
I have to press the space bar number of times (5 or 7) to run the playhead, to stop it also I have to press space bar number of times.
Oh, well anyway the guy in the video said "RAM preview" because that video was from 10 years ago when AE still had RAM previews. If you want to fix your playhead, try reinstalling, clearing cache, removing third-party plugins, etc.
I have done reinstalling. But I did not try clearing cache. Now I have third-party plugins but this issue persist from when I did not have third-party plugins.
Have you tried changing the shortcut from the preview panel? And you should still clear cache.. and possibly allocate more RAM.
Space bar & playhead works fine in Premiere Pro.