Variations from Basic Strategy

How important is it to vary from basic strategy when the count runs high such as staying with 16 vs 7 or higher? What about doubling down variations?

Varying your bet size relative to the count is the primary factor that "gets the money" for card counters. The wider the bet spread the more true this is.

Basic Strategy Depoartures that are keyed to the True Count are important in one and two deck games but is relegated to a lesser factor in shoe games.

Some plays are important, but most of the 200+ indices are worth only "chump change"

The top dozen or two plays capture 90+ % of the power of varying your card play.

See "The Theory of Blackjack" by Peter Griffin for the actual values for all of the plays. But better yet purchase and study "The Illustrious Eighteen" and "Fab Four" in "Blackjack Attack", 3rd ed, by Don Schlesinger.

I will tell you that the most crucial departure index is for INSURANCE. Knowing what to do with your 16 vs. a dealer's Ten is valuable. The play that you mentioned has little value. Remember that there are indices that aren't really worth anything.

Thanks for your thoughtful response. I will add most of the "Illustrious 18" in "Blackjack Attack" to my insurance variation. I do not plan to split 10's as it raises too much attention. Any thoughts on splitting 10's?

I agree that when you split 10's you get a ton of attention often but I do not completely write the move off.
Playing in a casino unrated and deciding that this would be the last shoe I play before moving on, I do not hesitate to split 10's if it is the proper play.
Playing rated in a casino I return to often a split of 10's is something I would rarely do but there still might be a time for it.