Welcome to the Corolla Forum! :thumbsup:

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arty::balloon:
As for lowering springs, there is already a plethora of information on this topic here. Use the Search function to find the threads and you'll have a boatload of information on it.
Lowering springs, (or any other aftermarket product), doesn't void a new car warranty. The federal Magnuson Moss Warranty Act law protects consumers in this regard.