'Practical English Usage' by Swan says:
Superlatives can be followed by an infinitive structure. The meaning is similar to an identifying relative clause (see 495).
He's the oldest athlete ever to win an Olympic gold medal.
(= ... who has ever won ...)
This structure is also common with firstfirst, secondsecond, thirdthird etc, nextnext, lastlast and onlyonly.
Who was the first person to climb Everest without oxygen?
The next to arrive was Mrs Patterson.
She's the only scientist to have won three Nobel prizes.
Question #1: Only the last example has the perfect infinitive ("to have"have won"). Can the other examples have the perfect infinitive as follows?
He's the oldest athlete ever to have won an Olympic gold medal.
Who was the first person to have climbed Everest without oxygen?
The next to have arrived was Mrs Patterson.
Question #2: Is the infinitive structure merely optional or obligatory?
For example, can you use V-ing instead as follows?
He's the oldest athlete ever winning an Olympic gold medal.
Who was the first person climbing Everest without oxygen?
The next arriving was Mrs Patterson.
She's the only scientist having won three Nobel prizes.