Hello, i am new here. This is my first post. This is a 1.5 months old thread, so i wonder if someone will read what i have to offer. Here is my two cents on this: Section IX does not require a CWI to sign off on a WPS/PQR/WPQR. Anyone who is designated to do this in the organization's quality program can sign on these documents. It could be anyone, as long as he is designated for it.
Though,since 2019 edition - Sec IX requires people responsible for 'supervision and control' of the welding qualifications to be designated, and their competence be established through training records, experience, training, etc. So, OP probably needs such a person, who is conversant with Sec IX, to perform the function of supervision and control. But not for signing on PQR/WPQR alone. That can be done by anybody.
Another thing, if the testing is subcontracted (that is, lab is not part of the qualifying organization), then that lab can only furnish the results. Whether the results meet Sec IX requirements is for the qualifying organization to determine, not the lab. Also, the function of certification of PQR/WPQR must be done by the qualifying organization; the lab cannot do it. There is an interpretation, IX-07-13 (qs 1), which made it clear - that the work of certification cannot be sub contracted. QG-106 itself states this too, that the function of certification cannot be sub contracted.