Feature Request: Modern Input Recording, Playback and Rendering

I am a YouTuber and Translator specializing in Japanese to English.
Normally my process is to play a game while recording it but lately that has become a problem because I now record in HD but some games get huge slow-down during playing in a higher resolution so I play it back later to record after streaming on Twitch in full HD, this was a test on Citra standalone which proved to be successful.
Streaming, I play the game in lowest resolution with input recording on, and after being done with streaming, I play the game back in HD, regardless of immense slowdown, I let it record to edit it later in my video editing software.

RetroArch looks to be lacking in this regard and playback of input recording is a hit or miss with unpredictable results.
My vision of Input Recording, Playback and Recording is to be able to play it back easily in RetroArch, edit input in a program or RetroArch to fine tune any minor problems possibly in real time, store the original RNG seed and allow for RNG edits in real time due to some games doing RNG on the fly because my tests show RNG ruins a playback, allow for just rendering without the need to play the input back in real time because I have other projects to work on.

As a video editor, a timeline is important, I think a great way to do TAS helps translators like me and with a visual timeline of button presses and errors showing any potential issues, helps to create a seamless series of videos.

You might be asking why anyone would do this, It's a business.
Translation takes time, some things come up which may be harder to translate, playing in HD while recording in the emulator itself is a nightmare, playing with my input recorded in Citra has allowed me to do what I call replayable recording.
Another feature I often seen missing is continued input recording, say you are doing per plot points or episodic, but what about input recording pausing at the end of the file and prompting you for another input recorded file to continue recording.
I stream on Twitch but playing in HD while streaming and recording is a disaster, that is why I come here.

Some games have multiplayer and I would like to record more than one controller for later playback along with their commentary recorded, is that possible?
My YouTube series Let's Translate, relies on this method very recently, is it possible the input recording and playback can use an overhaul?

Thank you for reading this.

The issue names no files, tests, or entry points. Start by locating RetroArch's existing input recording and playback implementation, then break the requested timeline, RNG control, rendering, continuation, and multi-controller behavior into a scoped milestone with explicit acceptance criteria; done should be defined for that milestone.