It is my understanding that the Sino-Soviet split was principally caused by unreconcilable difference in opinion in what the east's relationship to the west should be and not over what the role of the proletariat in the third world should be.

You are right that the struggle over leadership of the global Communist movement was a result and not cause of the Sino-Soviet split. But I would argue that the Sino-Soviet split was not even primarily over the issue of peaceful co-existence vs global revolution w.r.t the capitalist west. China in the 1950s only really cared about this issue over very specifically its own territorial claims, namely Taiwan. The attacks on the Soviets over peaceful co-existence largely came about because of the perception that the Soviets weren't backing China enough over a military solution in Taiwan. The Soviets, understandably, did not want to escalate a nuclear confrontation with the US over a piece of territory that it didn't really care about. The ideological struggle over peaceful co-existence therefore, was really an outgrowth of limited Chinese geopolitical objectives exaggerated by and escalated the Sino-Soviet split, rather than the core of the Sino-Soviet split.

The cause of the Sino-Soviet split really did come down to the interaction between Mao, Stalin, and Khrushchev. Mao genuinely did admire and model himself after Stalin. His economic policies of the 1950s were trying to replicate portions of the Stalinist economics of the 1930s, this was done over the objections of other senior party leaders. In that sense, he saw himself as China's Stalin. For Mao, "revolutionary Stalinism" was both the path towards Socialism, and to strengthen China's national power. Khrushchev's secret speech of 1956, though clearly not intended as such, was both a personal and ideological affront to Mao. The head of the Soviet Communist party and the global Communist movement denouncing Stalin was, after all, denouncing Mao's own brand of Stalinism as well.

This was a serious threat to Mao's domestic political legitimacy within the Chinese Communist Party itself. He had reasons to be on guard: reformists and moderates factions had won power struggles in eastern European Communist parties over Stalinists in the wake of the secret speech. Attacking Khrushchev and the Soviets was in a way, to shore up his own domestic ideological legitimacy. The issue of personalities also mattered here: Mao by all signs really did hate Khrushchev and consider him an ideological heretic on a personal level. It is difficult to see the Sino-Soviet relations souring so much without the personality of Mao leading China.

The Sino-Soviet conflict, though initially remained ideological and fought over paper and polemics between two sides, soon spiraled into a material geopolitical confrontation between the two Communist powers. By the late 1960s there was a shooting war between Chinese and Soviet border troops in the Ussuri River region. After US defeat in Vietnam in 1975, China and the USSR waged a vicious proxy war in southeast Asia through Vietnam and Cambodia, with over 100,000 Chinese troops invading Soviet ally Vietnam in 1979. China was deeply afraid that the Soviets were encircling China with allies on all sides and might one day invade with its much stronger army.

It's clear by the time of the US-China rapprochement in the 1970s that China saw the Soviets as the primary geopolitical threat to its own national security. The support for anti-Soviet movements in the 3rd world therefore, was part of China's realpolitik strategy to weaken the Soviet global position and ensure its own national security, with Communist ideology taking a backseat.

Source: The Sino-Soviet split by Lorenz M. Luthi