Pak and lap are easy for me to maintain, pak is an instinctive defense and lap is for me as well, perhaps too much because I am so damned used to transitioning to control techniques due to my occupation. Beyond that I will admit I tend to find myself using bil sau more than say a tan sau and if I bong it is usually a jamming bong during an entry. I will inadvertently do tan if my strike is intercepted by an opponent's strike but it's not something I instinctively do in and of itself. I am also find myself using a chuen sau quite liberally on entry as it can jam and cover simultaneously. In short I use many WC techniques but I have practiced to, for the most part, use the ones that are more compatible with natural human reactions.
As for when one should start sparring in WC it all depends on how one is trained in my opinion. Example, if one has adequate drills/san sik, the right students imo can start sparing before CK. YM himself said that a student competent in CK should be able to defend themselves and so at a minimum a student should indeed be sparing before BJ imo.
It is, imo, important to have students start at least "light sparing" when, as an instructor, you believe the student has two things. 1. Simply a solid foundation
2. Adequate control so they can indeed spar "lightly."
Doing the forms, drills, etc do not train the proper reflex reactions, they teach the skills that will be used when the proper reflex reactions are developed. You only develop the proper reflex reactions necessary for a fight under pressure in a dynamic environment and this requires sparring.