Try to get a shot of the bark up close, it should be easy to tell even on younger stems/ branches.
I mean, honestly it doesn't much matter in regards to the question you had whether it is Arakawa or regular Palmatum... Yes, you can chop below the lowest branches and it SHOULD still bud back if the tree is healthy. I would also agree with previous posts that it is best to do it in the Spring before bud swell, but I have done it in the late summer with fine results as well. Most Maples go into a state of almost dormancy during the summer in warmer climates anyway, then start growing again in the fall prio to Winter dormancy, so a trunk chop, repot, heavy styling, or even partial defoliation... Is probably not going to harm a Jap. maple much... At least not in my climate.