The Bulgarian agrarian figure Alexander Stamboliyski was imprisoned during WW1 for opposing Bulgaria's entry into the war, and he saw Bulgaria as a part of a future south slavic agrarian federation. When asked at his trial if he was a Bulgarian or a Serb he replied that he was a South Slav, and apparently aimed for a peaceful unification of the South Slavic peoples. He alienated the military and Bulgarian nationalists with a strong stance against war and territorial expansion. Stamboliyski signed Bulgaria's peace treaty with the allies as well as an agreement with Yugoslavia to drop Bulgarian claims to Macedonia.Wasn't there a Bulgarian agrarian party that advocated socialistic reforms while keeping mum on the monarchy? Iirc such a party won in the 1920s, but was kicked out by the army
It's hard to call agrarianism capitalist or socialist, agrarians advocated for the interests of farmers and peasants (land reform), but it often came with a right-wing celebration of rural people as preserving authentic religion and tradition, as opposed to materialistic urban society. Agrarianism's closest relatives are probably Distributist economic principles and Jeffersonian democracy.
The agrarian model of village cooperatives was more about keeping farm profits in their community, stabilizing income, and providing credit then it was about taking a side in a capitalism vs. socialism dichotomy. Being interwar Europe, agrarianism often came with large helpings of nationalism, especially when there appeared to be a large bolshevik threat or the landowners were from a different national group (Baltic Germans, Poles, etc.). Land reforms were the most radical in the Estonia and Latvia because they were a way to break the socioeconomic power of the Baltic German nobles and redistribute wealth toward future Latvian and Estonian elites.