The load balancer add-on was originally created to flatten review spikes, where new cards answered with the same ease would end up due on the same day in a predictable batch. That problem doesn't exist anymore since Anki now adds a random "fuzz" to the interval when answered.
Spreading out reviews may not offer you much, and can even be a disadvantage. If you find that there are too many cards to review every day, you need to decrease the number of new cards you add or stop completely. If you are currently not adding any cards, then the default behaviour is theoretically achieving the same thing: you set a maximum number of reviews per day, and that's all you'll get that day. Keep doing that until your backlog is gone.
Spreading out reviews may not offer you much, and can even be a disadvantage. If you find that there are too many cards to review every day, you need to decrease the number of new cards you add or stop completely. If you are currently not adding any cards, then the default behaviour is theoretically achieving the same thing: you set a maximum number of reviews per day, and that's all you'll get that day. Keep doing that until your backlog is gone.