In theory, if the add-ons don't affect an unrelated issue, then Tesla should honor the rest of the warranty. For example, if I tap the Tesla 12V battery for Texas blackout, the maximum Tesla can void the warranty is the 12V battery itself, not the failed drive unit, not the failed heat pump, not the Self-Driving Computer...
In reality, it's "Like whole-car-warranty voiding."
You'll be lucky if Tesla only voids the whole car warranty.
Others beg to pay, but Tesla wouldn't touch it if you have a problem unrelated to the aftermarket add-ons
(LiOn 12v battery, electric frunk/trunk).
So to answer your question: Lots of people do have add-ons, and they are fine. However, you are warned of the risk, so don't cry when you are being singled out!