will the method used to process the form change how I write HTML form code? :(

The value you provide here will affect the way the backend engineer would need to write their code, so it's important to coordinate with them. It might be the case that the file you're working in is a template that the backend will use to generate the proper value(s), in which case you won't have to worry about this value at all, but if you have to write it manually, the proper value here will probably be post in most cases, but it might be get. However, no matter the value that's necessary, there will be no difference in how you write your code. The only syntactical difference between an HTML form sent via post and one sent via get is that keyword. Everything else will be exactly the same