I'm afraid your "analysis" is approximately bassackward.
Lines carrying similar signals should be arranged as nearly parallel as possible. Signal lines should be shielded to contain the signals they're intended to carry. The same shielding that keeps the signals in keeps out similar signals from other (parallel) lines carrying the same frequencies, so the parallel alignment can be used.
Lines that carry noise or other signals that need to be excluded and that might contain frequencies outside the range that the shielding can handle should cross perpendicular to the line that needs to be protected.
Parallel lines couple "magnetically" and perpendicular ones have minimum coupling.
Gross example: the ignition wires in your auto engine must NEVER run parallel except when carefully separated in spacer combs. If a "wrong pair" are placed adjacent, or if they're parallel without proper spacing, the wrong cyclinder may "cross-fire" and the engine makes loud and objectionable noises and sometimes stops running.
Jon -
Windows runs a PnP search for new devices during each boot. After the boot and intital assignment for the devices present, plugging in a new PnP-enabled device will generally result in recognition, and an additional assignment will be made. For devices expected to be continuously connected, and especially for devices previously connected, it usually is preferable to have the device connected at boot, so that the PnP system can pick up previous setup details and attempt to use the same ones, although it can "negotiate" some changes if needed, and it does do a pretty good job of eliminating or otherwise handling conflicts.
Since USB and some other serial devices are expected to be "variably installed" it often is preferable to let the system boot and connect the permanent devices before a "first connection" of a device that may be connected and removed, so that the permanent ones get stable assignments, and only the new one has to be "fitted in." Once the new device has been given a place (esp IRQ/DMA assignments) PnP will usually attempt to keep the same setup if it recognizes the same device at a next reboot, or if it's properly disconnected and reconnected.
If a device is "turned off" the computer doesn't know it's gone, so it's setup assignments remain in place. When the same device is turned on, it sends its "PnP ID" to the computer, and it looks like a new device. The computer thinks the old one is still there, so a new setup has to be found. Since nearly all systems will have several shared IRQ/shared DMA assignments already, a conflict with at least one other existing device is nearly inevitable.
A "cursor lockup" nearly always means the mouse has died. In Sorcha's case, it's possible that unplugging the mouse, and plugging it back in might unlock things (a really iffy possible) but then there'd be the old speaker setup (redundant) plus the new speaker setup (obviously in a conflict) plus an old mouse setup (inoperable) plus a new mouse setup (maybe working, but probably not). Odds of anything continuing to work would be "low."
USB devices are somewhat tolerant of improper disconnect/reconnect simply because USB is designed to handle several connections, so there may be a "new name" that can be used when a device is re-connected and the computer thinks it's new. [Some USB devices do have a "device unique" ID that's sent to the computer at plug-in, but this seldom helps much, since the computer fails to reconnect it to the old setup (because it thinks it's already knows where the device is) but refuses to make a new connection (because it thinks that device is already connected).]
USB provides a "special method" via the "Safely disconnect" button that should be in the Startup Tray. You use this to tell the computer that a USB device is being removed. The same device, or any other USB device, then can use the "specs" for that connection if a new connect/re-connect is made.
USB device connections and removals can generally be done at any time, if the proper procedure is used.
ANY OTHER "pull the plug" or "flip the switch" kind of removal or addition of components should always be expected to require a reboot. In most cases, it's best to shut down the computer, make disconnects/connects with the computer OFF, and then restart the computer, except in the case of "brand new" things where the installation instructions tell you to do something different to assist initial device recognition.