(1a) In simple checks, we recently made the port parameter to tcp and tcp_perf mandatory, because port 80 has no particular reason for being a default port for TCP checks. Similarly here, in edit-discovery.png, we should always show the port used for TCP checks.
(1b) This is not seen from edit-discovery.png, but after creating a Zabbix agent check and creating an SNMP agent check after it, the SNMP OID defaults to the agent's key.
(2) When viewing a list of discovery rules, checks of the same type with a non-default port should have ports shown in parentheses. For TCP checks, the port should always be shown, same as (1a). See view-discovery.png.