Yeah.
Garling = Admiral Level
Pranks = Shanks = High Yonkou level.
Man Marked by Flames is Pranks. We know God Valley was on fire by the end of it, and that Shanks was on that island. We see Garling explicitly refer to "children" not just a child here in the VIZ: IE, he's talking to his kids, Shanks and Pranks.
Pranks got a burn scar on his face, just like Shanks got a scar from Blackbeard. Rocks was responsible for burning Prank's face (even if not directly) by invading God Valley; Rocks' successor, Teach, scarred Shanks. We didn't see Pranks scar when he talked to the Gorosei because it's on the other side of his face.
Pranks is despised by his own family and the Celestial Dragons for having the same face as the Yonkou, Shanks, who associates with what Garling considers to be complete trash. Since he has the same face as his brother, eventually, he was more or less exiled.
However, Pranks rivals Shanks in strength (two whole arms), and, as a result, was tasked with an impossible task in order to gain standing; find a Road Poneglyph to prevent what happened with Roger from occurring again.
The Man Marked by Flames can create water vortexes, or whirlpools. These can suck things either up, or down.
Obsessed with Roger and Shanks, Pranks scoured the world for the details of Roger's journey, to figure out where a Road Poneglyph could be. His luck struck when Myosgard returned to Mary Geoise with Otohime; Pranks, as a despised Celestial Dragon, was ordered to escort Otohime back to Fish-Man Island at Myosgard's request.
This is when Pranks discovered the Road Poneglyph on Fishman Island, and decided to steal it.
Pranks returned to Imu and the Gorosei as a hero, and was then tasked with guarding the Road Poneglyph via sea.
Pranks is strong enough to prevent anyone from stealing it, and even if they do beat him, Pranks can use his Whirlpool Fruit Ability to sink to Poneglyph into the ocean and send it flying via ocean currents so the people attacking won't be able to locate it afterwards.
Pranks is the Man Marked by Flames and at Shanks/Mihawk level, IMO.
Each Road Poneglyph has been guarded by a supremely strong entity in the One Piece World either connected to Rocks, or Roger/Joy Boy.
Kaido.
Linlin.
Zunesha (one shot Jack without really trying)
Kaido and Linlin had established bases in the New World, while Zou is a wandering entity that has no real mappable course... just like the man Marked by Flames, Shanks' twin burned by the Rocks Pirates attack of God Valley.
