This is too complicated for me to understand.
I suspect LHO was impersonated in MC, but also actually there.
CIA-hating Sandy Larsen's theory that evil, evil rogue CIA officers sent a 5' 7", skinny, blond-haired, blue-eyed, very-thin-faced, 30-something guy to Mexico City in late September 1963
to impersonate Oswald-impersonator Nikolai Leonov so that the FBI and the mainstream CIA would think the Soviets and the Cubans had collaborated with Oswald to kill JFK fails to take the following things into consideration:
The only two reasons the FBI and the CIA believed on 11/23/63 that a KGB officer at the Soviet Consulate in Mexico City by the name of Valery Kostikov was the Northern Hemisphere head of the KGB's assassinations and sabotage section, Department 13 of the First Chief Directorate, were
1) A Kremlin-loyal triple agent at the FBI's NYC field office, Aleksei Kulak (J. Edgar Hoover's shielded-from-CIA FEDORA) had told the FBI in 1962 that Kostikov's charge (pardon the pun) at the UN, Igor Brykin, was Department 13, and
2) The FBI's and CIA's TUMBLEWEED agent, a German national crop-duster from Snyder, Oklahoma, by the name of Guenther Heinz Schulz, told them in early 1963 that he had met with Kostikov and Brykin in Mexico City and that they had given him instructions regarding a sabotage operation (pinpointing targets) he was to fulfill for them in the US.
Schulz had been a recon pilot for Hitler, captured and interred in a POW camp by the Brits, recruited by the NKVD/KGB, and (ostensibly) recruited by the OSS/CIA after he was released.
I personally wouldn't trust him, would you?
It's interesting to note that in 2005, the CIA's official historian, David Robarge, wrote that the Agency never did determine whether or not Kostikov was Department 13.
Two other things to take into consideration in this whole Mexico City scenario is that:
1) the "Oswald" that Silvia Duran and Eusebio Azcue said they'd dealt on or about 9/27/63 at the Cuban Consulate was described by them in such a way that perfectly matched Raul Castro's and Che's mentor, short, blond-haired, very-thin-faced KGB Colonel Nikolai Leonov, and
2) the Soviet Embassy Security Officer who "volunteered" the Department 13-radioactive name "Kostikov" to Oswald or "Oswald" over a sure-to-be-tapped-by-CIA phone line on 10/1/63, Ivan Obyedkov, was described by James Angleton in his Church Committee testimony as a Kremlin-loyal triple agent, i.e., the CIA mistakenly believed it had successfully recruited him.