Hello @perlman. Ideal for your application is a bit subjective. As with wheat, the other aspect is the quality, or functionality of the protein. You can read more about spelt on BAKERpedia here: https://bakerpedia.com/ingredients/spelt-flour/
As you are making crackers, I would conclude that a lower protein would be more desirable, as in the cracker industry where wheat flour is used. Traditional wheat crackers are produced predominantly using soft wheat flour that is between 9-11% protein, most crop years. Various growing conditions will impact protein quantity and quality.