tls – Encrypts and SSL EV on the same domain

Yes, you can, with some reservations.

Normally, let-crypt certificates are valid for a single fully qualified domain name. Thus, you can create a certificate (DV) identified only by a domain for and a certificate identified by EV for your root domain.

Note that using a generic certificate and some multi-domain certificates is another consideration. Some certificate authorities (including LetsEncrypt) may issue a generic / multi-domain certificate that will also be valid for your root domain because the problem's certificates always contain a SAN (other subject name) that includes your root domain root domain when the certificate request. Check the SAN field of the certificate to make sure your certificate covers exactly what you expect and nothing more.

Some security notes however, pay attention to server settings that may apply to all subdomains, such as some cookies and HSTS configuration.