Due to the nature of updates, assuming you are using a version control manager like Git, you are best to skim through and compare the updated templates to see if something important was added/edited/fixed on an as needed basis.
However the docs do mention:
When you upgrade your application using
php artisan spark:update, any views that have been modified will not be updated. Instead, you will simply be notified that these views were skipped.
So they shouldn't necessarily be overwritten if they have been modified.
Docs @ https://spark.laravel.com/docs/10.0/client-customization