Anyhow I want to know that if we delete our posts ourselves, does it have a bad effect on our account and can we still get tagged or something or it is completely normal ?
Of course you can delete anything you want from your post history. It's your account and your have a choice.
But remember once you posted something on the internet it stays forever... so it's possible you will delete your post from bitcointalk but else where it will stay for example loyce club... or ninjastic.space or maybe in someone's photos as a screenshot:)
Anyway answering to your question in any normal scenario yes you can delete the posts. No, does not have any bad effect on your account.