Can I float power/energy whenever I want? If I would like to deramp from 10 to 6 runes can I?

Yes — you can float power/energy whenever you have priority or are in the middle of paying a cost. Both basic rune abilities have Reaction speed, so you can exhaust a rune for energy or recycle it for power in any priority window (your Main Phase, in response to a spell/ability, during a Showdown, etc.) and during cost payment steps. The resource sits in your rune pool until the end of your draw phase or end of turn (Rule 166).

Recycling is an activated ability on each rune — not something you need a separate card to do. So whenever you have priority, you can simply activate "Recycle this: Add [C]" on any of your runes. That power floats in your pool (and will be lost if unused), and the recycled rune goes to the bottom of your rune deck.

On "deramping" — yes, mechanically you can recycle runes just to put them back in your deck and reduce your active rune count from 10 to 6. Each recycle is a legal activation; you don't need a target or a reason beyond adding the power to your pool. The rune goes to the bottom of your rune deck, so you'd need to draw through it again to get it back.

However, there are two practical limits:

• You can only do this during priority windows or while paying costs — not mid-resolution without a cost to pay.
• At competitive rules enforcement, intentionally cycling runes with no game purpose other than to reshape your board could draw Slow Play scrutiny if it wastes time (Tournament Rule 703.2). But as a legal game action, it's allowed.