Socialist Republic of Vietnam
Economy
Vietnam mostly spend the 1970s and 80s rebuilding, and their economy, and in particular agriculture, began to stagnate in the mid-80s leading to market reforms. However, the Vietnamese government has never claimed they've ever built socialism, describing themselves nowadays as a socialist-oriented market economy.
Relations with China
Vietnam has had a rivarly with China going back hundreds of years, stemming from the desire of the latter to incorporate or subjugate the former. This has carried over into the period where both countries have called themselves socialist, with (the People's Republic of) China finding issue with Vietnam for being backed by the USSR, which the PRC had another rivalry with. This led the PRC to support Democratic Kampuchea, which attacked Vietnam in what came to be the beginning of the Third Indochina War, but then got pushed back. As Vietnam had already occupied a large section of Cambodia, the PRC attacked to Vietnam's north in hopes of distracting it and advanced a little, however the Khmer Rouge was overthrown by Vietnam regardless and a new communist government was installed in Cambodia, the People's Republic of Kampuchea, as the PRC retreated and both sides announced some kind of victory. To this day Vietnam is at odds with the PRC, however in terms of projects like the Belt and Road Initiative it is somewhat neutral. Perhaps the greatest animosity between the two countries in modern times is due to the South China Sea dispute, an oil- and gas-rich area that involves also the interests of Taiwan, Malaysia, the Philippines, and Brunei. The exact borders of control are rather unclear and so there are occasional clashes between the PRC and Vietnam, largely by fishermen.