Nikoda asks:
How much creative control do you have to give up to your editor/publisher especially as a new writer? For licensed properties like Halo or Star Wars the licensor has final say on everything. They may value your creativity and ability to write, but you have no control over the project.
For non-licensed intellectual property, that is stuff that you've developed on your own, you'd be surprised how much creative control you retain, even as a new writer.
First and foremost (and this may or may not be a good thing) agents and acquiring editors today simply don't have time to take on a project that isn't in their opinion near perfect i.e. needing many changes.
In some cases, an editor/agent may turn down your project, and give you specific reasons. In that case it's up to you to decide if you wish to address those issues and change your project, and then resubmit.
Second, there are a series of checks and balances during the publishing process. You turn in a manuscript. Your editor gives you feedback, and you accept or reject these suggestions. Either party has the option during these checkpoints to refuse to continue in the publishing process. It is extraordinarily rare to get this far and have things fall apart. The only time I have seen it happen is when the acquiring editor leaves and a new replacement editor asks for sweeping changes (this event is lovingly called an “orphaned” novel).
Bottom line: barring unusual circumstances, if someone bothers to buy your novel they are not going to change it that much.