"Do you don't think the toxic parents ever think "shit, I think I might be a really awful parent?"
That thought never occurs to them because they lack both empathy and insight.
"Sometimes if I argue with/am overprotective of/anxious about the DC, I think "oh god, am I one of those toxic parents people write about?".
No you are not if you are thinking like this. I would think you also apologise for any mistakes you make as well as taking full responsibility for your actions. Toxic parents never apologise nor accept any responsibility for their actions.
Whether you want it or not, your parents plant mental and emotional seeds in you. These seeds grow as you do. In some families, they are seeds of love, respect and independence. But not in all of them. In many others, they are seeds of fear, obligation, or guilt. There are many parents who act abusively towards their children, and such toxic behavior becomes consistent and dominant in a child’s life.
All parents make mistakes in upbringing. That’s normal, since there’s no perfect parent.
But there is a clear line when too many mistakes, especially repeating abusive behavior towards children, lead to a toxic home environment that does severe emotional damage to an innocent young person. Parents who carry a promise of love and care, while at the same time mistreat their child, are called toxic parents.
Almost all toxic parents say they love their children, and they usually also mean it. But love involves much more than just expressed feelings. Real love towards children is also a way of behaving.
What toxic parents call love rarely comes up as nourishing, comforting, encouraging, respectful, valued and accepting behaviour. Toxic parents usually do extremely unloving things in the name of love.