It occurs to me, that hosting a website on www.domain.com will result in duplicate, unnecessary DNS lookups if www is a CNAME and not an A(AAA) Record. If the CNAME points to another CNAME, things start getting messy.
WWW as an A Record: one lookup for the A record
WWW as a CNAME: one lookup for the CNAME, plus (at least) one for A record.
For the purposes of SEO, for which which speed is a measure, will this matter? Should I change all my CNAMEs to A records?