If you are preparing for 2020 then I am sure by now you must have invested a lot of time in these subjects. Still I would like to say something about this combination.

CS is a subject that must be opted if one has a strong educational background in it. Since you have opted this subject I guess you do.

Punjabi is an evergreen subject. Always scoring. So no issues there.

P Ad, I Law and IndoPak are subjects which I think are likely to be targeted in CSS 2019 based on what I have read on the forum. Now I am not sure if this is a good thing or a bad thing for someone who is appearing in 2020.

Having said this, I think one’s interest and educational background should be the primary factors affecting one’s decision to opt any particular subject. Availability of relevant material and ‘scoring trend’ though can not be ignored.