How do Shopify owners deal with returns and complaints of non-delivery?

I still haven’t signed up for a Shopify shop, but I’m very interested in doing so. I thought about drop-shipping, but it seems like it would take a very long time for items to reach customers, and don’t understand why anybody would wait so long. I’m still trying to source items to sell. But I think I would like to handle shipping myself.

What I’d like to know is how people deal with returns. And how do people deal with fake complaints of non-delivery? Getting a signature for each item sent would be expensive. Plus it might be a nuisance for customers who need to be at home to receive the package.

Thanks.