Google's suggestion is just an example. You can theoretically use any email address you like. It should not include your actual name, in my opinion.
Reports that are sent to the rua address contain XML files consisting of, depending on how many emails you send out, many hundreds of lines of email authentication data. And these reports are coming daily, per mailbox hosting provider. It is generally best to automate the flow and visualization of these reports in a tool, specifically built for just that.
So, the email address should not contain a name of an actual person and does not have to be in your registered domain at all. This also makes for a poor email address to send SPAM to, since, most of the time, this email address is not likely to be ever opened by a human. Rather a service that will strip the XML attachments for processing.
Do keep in mind that if you want to have the aggregate reports for
domain-x.com sent to
firstname.lastname@example.org, you'll need the owner of
domain-y.com to create an additional DNS
domain-x._report._dmarc.domain-y.com IN "v=dmarc1;", authorizing reporting organizations to send their reports for
domain-x.com to a mailbox in domain
domain-y.com, as explained here.