signing is usually based on the value of the item, if its high value you will need to sign, and fake sign so if they say you signed for the package (if they do DNA) you can say thats not my name so I didn't sign it and idk who that person is who did.
you cant make it so you dont have to sign again its based on value of the item. i dont have to sign for air pods from apple but for my Iphone I did.
yes the refunder will user a method. a good refunder has shop specific methods instead of just saying DNA or partial but yes most will do DNA/partial/empty box. they just email/call/live chat with the company and say one of those methods.
investigates are based upon the store, item cost and method used/ ive had many investigations and everything has been fine/normal shipping wise just space refunds apart/ some stores dont investigate with the carrair and some do.
most companyts will see you used a reship and not refund you. just use a drop or real address, its fine to use a real address as long as you dont do it like 5 times a week.
chaining reships is dumb and expensive as reships are like $30 just to ship the item.
this is all stuff you talk to your refunder about before you use their server most of the time.