So I've run a couple campaigns testing out possible Nationalist China strategies about as far out as mid/late 1938, and I'll share my observations here.
In my first attempts, I went with the United Front. The main benefits of this approach seem to be keeping Mao and Sheng out of the Comintern and gaining expeditionary forces from the warlords. These expeditionary forces are not especially helpful and I found keeping them supplied was a waste of precious IC that would have been better spent on my air force or on upgrading my own divisions. The war went reasonably well early on while Japan was still affected by Marco Polo Bridge maluses, but they went away faster than I could remove Army Corruption and I ended up pushed out of Beijing and Tianjin by mid-'38.
Afterwards I took a couple stabs at pacifying the warlords first. The result seems to be that two of the five warlords accept and the other three don't- even if you immediately rush for this focus, there isn't much time before Marco Polo and priorities have to be set. The most success I've had has been with annexing Guangxi- the resources lost to trade net a significant number of civs and dramatically improve your industrial development, and my army came out of the war with many Seasoned and a few Veteran divisions as well as almost enough experience to start the first round of army reforms. This meant significantly better army performance at the start of the war with Japan and much faster industrialization. If I had trained more divisions from the start, it may have been possible to simultaneously invade Shanxi or Xibei as well for more army experience.
Overall, annexing Guangxi seems to be the optimal early outcome, puppeting Guangxi seems to be second-best, followed by the United Front and with the worst possible outcome being to have no leadership over Guangxi at all. It's so much more populous and resource-rich than any other warlord that the rest are almost irrelevant from a military standpoint. Either way, the Nationalism and Army Reform branches seem mandatory in the early game, especially in light of the low returns from other focus branches.
In my first attempts, I went with the United Front. The main benefits of this approach seem to be keeping Mao and Sheng out of the Comintern and gaining expeditionary forces from the warlords. These expeditionary forces are not especially helpful and I found keeping them supplied was a waste of precious IC that would have been better spent on my air force or on upgrading my own divisions. The war went reasonably well early on while Japan was still affected by Marco Polo Bridge maluses, but they went away faster than I could remove Army Corruption and I ended up pushed out of Beijing and Tianjin by mid-'38.
Afterwards I took a couple stabs at pacifying the warlords first. The result seems to be that two of the five warlords accept and the other three don't- even if you immediately rush for this focus, there isn't much time before Marco Polo and priorities have to be set. The most success I've had has been with annexing Guangxi- the resources lost to trade net a significant number of civs and dramatically improve your industrial development, and my army came out of the war with many Seasoned and a few Veteran divisions as well as almost enough experience to start the first round of army reforms. This meant significantly better army performance at the start of the war with Japan and much faster industrialization. If I had trained more divisions from the start, it may have been possible to simultaneously invade Shanxi or Xibei as well for more army experience.
Overall, annexing Guangxi seems to be the optimal early outcome, puppeting Guangxi seems to be second-best, followed by the United Front and with the worst possible outcome being to have no leadership over Guangxi at all. It's so much more populous and resource-rich than any other warlord that the rest are almost irrelevant from a military standpoint. Either way, the Nationalism and Army Reform branches seem mandatory in the early game, especially in light of the low returns from other focus branches.