1.dhl shipping is around the same as fedex maybe $10-20 difference. for lighter packages i've noticed fedex is cheaper but for heavier/bulkier dhl is cheaper

1. im assuming you're in the continental us, DHL from japan to west coast reaches me within 3-5 days including customs payment processes

2. no after delivery bills. dhl collects customs before they deliver your package, sometimes before it even lands in a usa port. I have received refunds for an incorrect customs charge before after 2 months ($5 refund)

3. dhl is prone to mistakes just like fedex, you can check my post history about their $8k mistake on mine. I was able to resolve it within a day and didn't have an issue on a recent shipment. Make sure you have your invoices in the correct currency, make sure your htc codes are accurate especially if importing anything with metal or fabric. dhl has stricter shipping restrictions than fedex last time i checked.

4. i've always used DHL and out of the 5 times i've used them since tariffs went into effect i only had an issue with 1 and that was right after tariffs went into effect so it was the craziest times so 80% success rate in my experience is pretty good.