I just tested to hide the "off-switched" lights in my pinball table by stopping at an empty frame. I did it with "tellTarget" as this is supposed to be 25 times faster than dot-syntax or "with" (flasm site).
Anyway the whole game slowed down.
In this case the power to switch states by "gotoAndStop" or "attach/remove" drag more performance than just keeping all lights on the stage and changing there _visibility.
Seems like: if you have a lot of on/off switching to do fastly, you better use _visibility; otherwise i guess displaying an empty frame ist better, because it (hopefully) costs less drawing time. Perfect seems attach/remove, if you have the CPU Power to do so. Offstage-clips should be removed anyway.
3 ways to get nothing. :-)

Concerning scrolling, i think it is best to place off-screen-clips on screen again by just altering their coords instead of removing/attaching - if your clips allow to do so due to their content.