DSCP is used for marking, within the TOS which is in the IP header.

The preempt command enables the HSRP router with the highest priority to immediately become the active router.

Cisco IOS XE supports the Yet Another Next Generation (YANG) data modeling language. YANG can be used with the Network Configuration Protocol (NETCONF) to provide the desired solution of automated and programmable network operations. NETCONF(RFC6241) is an XML-based protocol that client applications use to request information from and make configuration changes to the device. YANG is primarily used to model the configuration and state data used by NETCONF operations.
Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/16-
5/configuration_guide/prog/b_165_prog_9500_cg/data_models.pdf
Note: Although NETCONF also uses XML but XML is not a data modeling language.

A maximum transmission unit (MTU) is the largest length of a packet that can be transmitted out of an interface toward a destination.
maximum receive unit (MRU) is the largest packet size that an interface can receive, so it's an ingress interface parameter.
https://www.networkers-online.com/p/understand-mtu-and-mru-the-full-story