Right now, while the price is low or rising, it is more efficient to power up 100%.
You can find that setting in the advanced tab of your posts, or you can make a template that will have it each time.

The reason it is more efficient to power up is that were the price to rise it is better to be in hive than hbd as you get less hive for your hbd as the price rises.
When the price is dropping, the opposite is true.
You can buy more hive with your hbd later as the price drops.

Here is another place to learn about hive.

There are lots of moving parts in the math of the hive.