I’m not 100% clear on what you’re looking for.
What to you mean by:
Normal WYSIWYG wordpress allows you when you first create the field to say whether or not you want it to put out HTML or just pure text.
I don’t have any knowledge of adding a wysiwyg field in WP other than using ACF to do it, so any documentation you can point me to would probably be helpful.
ACF4 uses a different editor than the main WP editor. ACF5 uses the same editor. There is a significant difference between these two versions of the plugin. The developer is working on releasing a free version of ACF to WP some time this year.
