Cannot determine anything best with the given nerf. Because, need to play the event from day 1 with the given nerf to give you solid answer. Now it is half cooked meat, not possible to distinguish anything easily with proper facts. Without facts, I can give you free advice, which is like don't trust free spawner very much and till rush quests available use the energy until opening gold chest or max energy chest daily and don't spend anymore on that day. Keep this behaviour on the board and concentrate on event quests till rush getting over. After rush quests, use the same approach till the last 4 or 5 days of the event. Then on the last four days of the event, unleash your energy on the board if any daily prize satisfy you to open any of the chests. That's all and remember this is my free advice without any facts and there may be lot of hurdles to follow this, it's upto you.
If I was
@Juber, I might have told you to look on "Tips and tricks" shared in the announcement and play the game with your own strategy.
Also in tips and tricks, cleverly answered for lot of problems or expectation in the game. Like, free gem spawn cannot come with key parts, will lose gems with keys if they do manual reset without clearing board, after clearing board doing reset and board has 3 key gem will give one key only and mainly mentioned to stop attempting to clear board. There are few more hints, but the given nerf already does the heavy damage. But they are keeping silent. Just one more week, will move on for other things.