Good question.

The Korean War saw a lot of nations. The UN forces had Korean ( obviously )American, British, Indian, Turkish, Belgian, Dutch, Swedish, Japanese, and even Ethiopian troops.

the majority of units in the Korean War were South Korean ( ROK ) and American. And by majority I mean the vast majority. The ROK troops had been working with American generals for some time and since they used the same doctrine, American commanders had no problem using them as they would American units. When the French and British eventually arrived, they too were very similar in American doctrine, so American generals used them as well the way they would American units and in American doctrine. Units from other nations however were sort of sidelined. The reasons were various but often had to do with better combat effective units being available. But when these were not at their disposal the American generals had no problem using these other units in the operational level. One prominent example comes from a Turkish Brigade or just known as the Turkish brigade. It was fighting under the US 25th infantry division. It was very good at fighting and this surprised some people as Turkey wasn’t in WW2 and these troops were very green. The US commanders even used them in the operational level as a fire brigade ( a unit sent to hold an enemy breakthrough till more units arrive ) unfortunately they were wiped out, but it shows the US confidence in using UN troops.

That being said, the other units sent to Korea from other nations were small and yes did see action, but not as often as ROK and US troops. There combat effectiveness varied on nation and as far as equipment went, some were using their own nations or equipment from other UN nations like the US, UK or France.

As far as encryption methods I can’t speak to that but I’d assume everything would be dominated by US and ROK forces with these other nations playing a minimal role.

As far as tactical doctrines went, it varied on a couple of things. The Chinese fought using a human wave/soviet doctrine of constant attack and the North Koreans fought a more traditional soviet doctrine. The UN troops attached didn’t really have to worry on the operational level ( again dominated by American ) but they did have a go at it on their own on the tactical level. And at first they had trouble, but given time they performed very well fighting in very similar tactically as American units. Whether this is because they were controlled by US commanders or because they were both fighting the same enemy or a combination is unknown to me but I assume the latter.

So in summery. These units ( Not US, ROK, UK or French ) were in too small of scale to be used on the operational or strategic, and often sidelined for more trained forces from nations mentioned above. But they did see combat and had issues at first but eventually did decently well in combat ( some didn’t and these were made noted by UN planners ) They would be supplied by nations mentioned above ( not by the South Koreans though ) but were not of priority and carried their own nations equipment at times as well. But everything was fought under American doctrine and they were used in those roles and eventually evolved to fight that way.