You can register .ro domains and every Romanian extension (.com.ro, .info.ro, .org.ro, .store.ro and more), plus international ones such as .com, .net, .org, .e...
DMARC can help limit unauthorised use of your domain in the visible sender address. It relies on SPF and DKIM checks and their alignment with the domain in the From field. It does not prevent every fraud attempt or stop someone using a domain that looks similar to yours.
Before adding a TXT record at _dmarc.example.ro, identify every service that legitimately sends email on your behalf. Follow your email providers’ instructions for SPF and DKIM. You can start with a monitoring policy and review the reports before applying restrictions. Introducing a strict policy without checking your setup may also affect legitimate messages.