The orders in the two programs may be different, yes. I don't think the order Opus uses has been documented anywhere (not sure about Explorer).
Context menus with a lot of items are going to be a mess whatever order the items are added, so removing unwanted or rarely used items, or moving them into a submenu, is the best way to tidy things up.
The linked post covers things you can do to only affect Opus. If you want to remove some items system-wide, and the programs adding them don't provide an option to do so, you can use ShellExView for shell extensions and the file type editor (or regedit if preferred, but be careful. of course).