Dylan,
Body scissors are a legal maneuver even in USAW. Any move not specifically allowed by NFHS rules would be part of the USAWKS Modifications, of which there are none specifically related to actual wrestling anymore. Way back in the day USAWKS used to have an uncontrolled high bridge modification, and a few others. These days wrestlers in the federation can do any move that is otherwise legal at any other level by folkstyle rules.
Head scissors are not allowed with or without an arm. Figure 4s to either the head or the body are illegal.
As an aside however, NFHS rules prohibit: Rule 7-1.u any hold/maneuver used for punishment. Referees must be very vigilant when a body scissors is applied and make sure it is not being used for punishment as the potential for injury is heightened with that particular move.
Hopefully this clears this up for you.