Good questions:
1. I do the harder work better (better quality, more rest)
2. I do the easier work more (more repetitions, focus on mechanical efficiencies, etc)
3. I like to push a model or program until the improvement levels off, then stick with it for a few more weeks, before changing by degrees.
4. As for different and variety, what I find is you can keep it fresh by experimenting in warm-up, cool-down, and recovery days – different exercises, different energy systems, and so on.
5. Focus on strengths. Weaknesses can usually be addressed along the way – and again through doing more of the easier work. The exception is if the weakness is a major limiting factor. What I’ve discovered in the past several years, where (after 8+ years off) I got back to the condition I was in as a collegiate all-american – now in my mid-30’s – was that strength/power was probably my biggest limiting factor in almost all my events. Kept me from hitting and holding positions, had less total horsepower, etc. Now that I’ve begun to get strength to “strong enough” (or at least close) – tendon health and elasticity are increasingly limiting factors, and am going to begin doing more about that…. Get your weakness to “good enough” and then really emphasize your strengths.