If two Ekkos die at the same time, am I able to resolve one, float all my runes energy, then ready again off the second?

Yes — two Ekkos dying at once means two separate Deathknell triggers, so you can do the "double-dip" twice.

Both triggers go on the Chain (you choose their order), and they resolve one at a time. First trigger resolves: recycle that Ekko, ready all runes. With the second trigger still on the Chain, you control the newest item and have priority, so you can exhaust all your runes at Reaction speed to float energy. Then the second trigger resolves: recycle the other Ekko, ready all runes again. Since each Ekko is a separate game object, you can recycle both — the "can't recycle the same card twice" limit from FAQ #7490 doesn't apply here. You end with all your runes ready and double-floated energy in your pool until end of turn (Rule 167).