How to manually remove wifi connection details I have a problem with my rom where it does not successfully "forget" wifi connection details and so I find myself connected to the wrong unwanted network.

I had a look at this thread which showed the location of the setting but I'm unsure if it's just safe to delete it, or I need to edit it.

I do not mind having to remove all wifi settings if that's the case.

Thanks.
You cannot manually clear Wi-Fi connection details in a non-rooted device other than going to Wi-Fi settings and clearing all the connections and general settings or doing a factory reset which would bring everything to default factory state. 

The reason is simple. You, a non-root user, are not privileged to delete the files holding the Wi-Fi connection details and settings. 

As for the link you mentioned (a post and not a thread), the files settings.db and wpa_supplicant.conf are inaccessible to a non-root user. You would observe  permission denied error if you try to enter their parent directory. 

However, if the device is rooted, then there is no restriction on you to access them. Simply download a root file explorer, access those file's parent directory, and delete those files. Of course, copy them in PC before deleting, to be on safe side.

And before you even attempt to copy them  into PC, make sure a custom Recovery is installed already so that you could save yourself from a mess if things go south after deleting those two files.