Afghan - No decisive small benefit to CP. The British probably keep more Indian troops in India, and the war with the Afghan will consume some financial resources. The only way this has a big impact if the UK for some strange reason makes the Afghan area the major campaign area and diverts many corp to conquering and garrisoning the country.
China - Not sure terribly realistic. I would go small benefit to CP, like Afghan because UK resources will be drawn to area. Major butterflies in post war era as Japan will grab a part of China in 1915 and not leave.
Romania - Depends on when comes into war.
1914 - Messes up Russia mobilization plans, and means a lot less pressure on A-H. With an extra army or two sent to Romanian border, maybe the A-H part does not collapse so badly, maybe even it holds without major surrender of troops. A lot would depend on Russia reaction to Romania. Any improvement in A-H performance likely butterflies away Italy, so decisive for CP. Russia will have real trouble changing its mobilization plan, and this cause chaos with logistics.
1915. Assume after Italy enters war and German HQ decide to make Poland a 1915 focus. The Russians will face pressure to move again one, maybe two armies to the Romanian border. Likely even greater success by German and A-H in offensive, but since the HQ wanted to make the French front the main front, the Germans may still stop near where they did in OTL, and move the extra forces to attack in the west. This is a bit trick call, because basically, and small country or Russia first strategy wins the war, and French first plan tends to lose the war. 1916 will be interesting. With the Russians forces spread over even a longer front, does Brusilov even launch an attack? Does Romania do ok against the Russians, or does Germany need to send troops to reinforce the Romanians? What is done with the Bulgarian Army? The CP have interior lines of communication, so they have many many options. This is likely a CP stalemate/victory, but if the CP does not take advantage of the extra resources before 1918 and America is still in the war, it can still go against them.
1916 - Much like 1915. Brusilov offensive likely cancelled, as perhaps combined Bulgarian/Romanian Armies make progress in the Ukraine. Germany will likely use reserves used to stop Brusilov instead to attack on west. Most likely, Germany squander this advantage, even though if Russian army is not as good as combined Bulgarian/Romanian armies, losses in food producing regions of Ukraine hurt a lot. I would go Entente still win, but butterflies or brilliant use of the extra resources by CP could win the war for them.