In many partnerships, I play double of a strong NT opener as penalty (mostly because I like a simple NT defense I'll remember).  When it comes up I find partner and I are often not on the same page and either partner pulls a profitable penalty double because he (unsurprisingly) does not have too many values or on the flip side, he sits and we are -180 (or whatever).  The lack of good results from playing this treatment has made me want to drop it.  I found the notes by Frances Hinden I found here https://www.bridgebase.com/forums/topic/51777-follow-ups-after-a-penalty-double-of-1nt/ useful, but think some of the issues I have are a little more basic.  Here is a (non-exhaustive) list of questions I have for those who (preferably successfully) play penalty doubles of NT openers (and I assume that's most of you against weak NT openers):

1. What hand types make a penalty double?  Just strong balanced hands or can you have something like KQJ109x Axx AQx x?  If your X shows a balanced hand, how do you show a strong unbalanced hand (this may depend on your overall defense I suppose)?
2. Assuming LHO passes (either forcing XX or not), with what hands is partner allowed to pull the double?  Does your answer change if they redouble for business?
3. If partner pulls, what do his bids mean?  Do you play NT systems on (and if X can show an unbalanced hand, do you make any adjustments to your NT system)?
4. How do your answers change if you are playing against a weak NT (say 12-14) or a mini NT (say 10-12)?
5. How do your answers change if doubler is in balancing seat rather than direct seat?