Would a light designed for use outdoors still use a standard fixture box? The fixture box will be attached to the joists under the soffit. An outdoor rated fixture box is only needed when the box itself will be exposed to the outdoors, correct?

I am replacing an old bedroom light switch with an anywhere switch to add an extra remote switch. When I pulled the old switch from the box there was what I thought were 3 black wires coming out and 3 white wires inside the box nutted together. Yep on the 3 white wires in the box. Looking at the box, one black wire comes out on the right - kay no problem. On the left where I thought were two wires, it was actually one wire coming out and is looped around the left screw on the old switch and then nutted to another wire which then went back into the box. I've alway read that if you re-wire something as it was originally wired your OK. I'm pretty sure I can snip the left wire that goes around the screw into two and tie them together with the black wire coming out of the new switch on the left. Just wanted to make sure before I sniped.................. Hope this is clear and thanx for any help Kristyna