Proper Form For Reverse Planche

I see some people do reverse planche with their legs horizontal, others do it with extreme arch like a bridge with the feet off the ground. What's good and proper? Also, is hollowback synonymous with reverse planche?

Hollowback is very similar.

Reverse planche in the women's gymnastic world typically is with the feet arched pointing to the opposite direction of the chest as a counterbalance. I have seen it worked with an extremely open shoulder angle and a planched shoulder angle as well as with the legs in a straddle split. Look it up in the FIG code for women's artistic gymnastics.

There really is nothing cut and dry about this.