The easiest option you have is to find these lines in redactor.js, and hide them with inline css. It will preserve the state of the image float.
+ '<label>' + this.opts.curLang.image_position + '</label>'
+ '<select id="redactor_form_image_align">'
+ '<option value="none">' + this.opts.curLang.none + '</option>'
+ '<option value="left">' + this.opts.curLang.left + '</option>'
+ '<option value="center">' + this.opts.curLang.center + '</option>'
+ '<option value="right">' + this.opts.curLang.right + '</option>'
+ '</select>'
Starts at line 7164 in my unmodified v9.2.2.
If you just remove those lines redactor will always set the image float to default. As well the margin and display too. But you can tweak that behaviour in the imageSave method. (#6700)
$el.css({ 'float': '', 'display': '', 'margin': '' });