Microsoft Word Remote Code Execution Vulnerability

Is the Preview Pane an attack vector for this vulnerability?
Yes, the Preview Pane is an attack vector.

According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution?
The word Remote in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally.
For example, when the score indicates that the Attack Vector is Local and User Interaction is Required, this could describe an exploit in which an attacker, through social engineering, convinces a victim to download and open a specially crafted file from a website which leads to a local attack on their computer.

According to the CVSS metrics, successful exploitation of this vulnerability could lead to major loss of confidentiality (C:H), integrity (I:H), and availability (A:H). What does that mean for this vulnerability?
An attacker who successfully exploited this vulnerability could gain high privileges, which include read, write, and delete functionality.

Security updates
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.0.5435.1000 — https://support.microsoft.com/help/5002542