Your visitor is on a phone, in the room, staring at the window they want gone
Design for a one-handed thumb on cellular data in a living room, because that is where most of these sessions actually happen.
Type sizes that survive a bright room. Tap targets that do not require aim. A phone number that dials on tap and sits in a sticky bar rather than only in the header.
Speed is a conversion feature here, not a technical vanity metric. A hero video that takes four seconds to appear has already lost a share of the people it was meant to impress.
Assume the visitor is comparing you against two other tabs. Anything that takes an extra tap to find is effectively not on the site.
Desktop still matters for the second visit, often with a spouse, usually reading in more detail. Build mobile first and let the desktop layout carry the longer proof.