I've had requests from the #writingcommunity about editing. New authors sometimes aren't sure where to start or how to go about it. It's extremely intimidating to look at the entire finished book at once, so having a process to edit helps us see it in smaller, more manageable pieces. I'm going to give you two perspectives: one from a writing instructor's point-of-view--basically what I teach my students for all types of writing--and then from an author's point-of-view--meaning the exact steps I've taken with two different publishers.
Revision-- the focus is on global issues, meaning you look at the ideas, organization, content. The key is to NOT look at grammar or sentence structures.
Edit--here's when you look at sentence structures, the flow, fixing word choices and grammar, polishing it up. The trick is to read it aloud to hear problems.
Copyedit--this is when you hyperfocus on grammar, format, word choices trying to find any remaining mistakes. The key is to print it out so you can correct it like a teacher--you see things differently when switching mediums.
As you see, this starts global, looking at it as a whole, then works to narrowing the focus. If you try to do it all (and are not an editor or teacher), it can be extremely overwhelming.
With publishers, I've had three similar levels called different things but in a sense have the same concepts:
Developmental--they look for important content issues, such as plot holes, and discrepancies in timelines, long lulls, info-dropping, character motivation, consistency, and arcs, etc. This is much like the revision process in that it seeks to fix global issues.
Line edits--this is focusing on word choices, grammar, cohesion what you think of when it comes to an editor trying to fix everything in your work. It is pretty much the same as educational editing, but it is very focused, looking for everything.
Copy edits--this is another round of looking for grammar, typos, but also formatting, spacing, every little detail of how it looks on the page. Usually, the publisher will have a proof copy to read through. seeing it in print, in the novel makes it easier to see errors. Sometimes this is considered a fourth step, proofing.
This looks a global and specific issues, but I notice editors tend to do it more organically, mixing these steps together at times--particularly if they don't have too much to note developmentally, they'll get ahead. The idea is roughly the same in the end.
So how much do you edit? That is up to you. I'm an English professor who teaches grammar and yet I make a ton of errors in a rough draft. I also am a pantser and find that I write faster than plotters, but must revise more for those plot holes I create. Usually, I revise twice, then edit once, send it to a couple betas, edit, copyedit, and then submit. My publisher then does the above steps developmental, line, and copy edits/proofing. That's a minimum of eight rounds of editing after the initial rough draft. The thing I notice most when books are not professionally edited is not just grammatical mistakes, but also more global--long lulls, strange character behaviors or forced motivations, time incongruity, info-dumping, and more. It cannot hurt an author to seek professional advice and can help them see issues easily overlooked.
The takeaway? Do all three rounds as much as needed before querying. Breaking it up in 3 stages makes it less daunting. Know when to let go, when to seek help, and always have some kind of pro help you. No matter how good of a writer you are, you cannot catch all your mistakes or be unbiased. Professional editors even have editors look over their work