I wouldn’t bother with the ESRB rating unless you intend to somehow do physical distribution through a retail chain. For a download product you just have to fill out a questionaire to get a rating and they will be more concerned about microtransactions and online interaction than content. If your game connects to the internet or has microtransactions you won’t likely get an E rating. They are not going to play your game or even look at a video. They will issue a rating based on your answers to their form and maybe, not likely, but maybe your game will get audited months after release. Also, not sure about this, but you may have to pay for a rating on PC. I know they started a free rating service for digital distribution but AFAIK it only applies to walled garden services like Playstation, XBox and Nintendo that have a qualification process for every game they distribute. PC is a free for all even with Steam.
If you get picked up for console, the publisher/platform holder will help you with the ESRB process.