hi jerry, I'll help you :)
as you have seen, the voting power and voting strength are different. By default small voters will always use 100% strength and this act of voting takes away 2% of their current power , so the lower your voting power goes, the smaller each vote is worth and the longer it takes to drain it even more to a minimum of 0.01% voting power drained per vote.

Let me give a series of examples to make it simple:

• 100% voting power, 100% vote strength = 98% remaining power
• 50% voting power, 100% vote strength = 49% remaining power
• 20% voting power, 100% vote strength = 19.6% remaining power
• 10% voting power, 100% vote strength = 9.8% remaining power
  etc.

this also scales the other way:

• 100% voting power, 75% vote strength = 98.5% remaining power
• 100% voting power, 50% vote strength = 99% remaining power
• 100% voting power, 25% vote strength = 99.5% remaining power
  etc.

and then you must note that voting power recharges about 20% per day, so you could do 10 MAX STRENGTH upvotes per day at 100% power, and if you are at 50% power you can do 20 and sustain there, they will just be worth about half as much on average.

Note no single way of doing this is strictly better in terms of total output, it's just a different form of concentration or spreading the votes around, the primary thing you need to optimize is keeping your voting power from recharging to 100% and staying there for extended periods of time.

Hope that helps you (or anyone else with the same question) ^_^