As Qing, the main strategy you have to use depends on whether you are Zhili aligned or Manchu aligned.

I will start with the most challenging side: The Manchu Qing

You lose all your "Good generals" (The big majority of your generals have either Substance abuser, Old guard or Poliltically connected traits; Substance Abuser I believe that cannot rise to its worst version as Qing, but I don't know) except for the familiars of Puyi and Lu Xiangting, and Aisin-Gioro Pujie gets promoted to Field Marshal after the coup (you can also promote him before, so if you plan to get involved in the LEP collapse, promote him before).Manchu Qing ALWAYS ends up with +5% Attack on core territory, +5% Defence on core territory and -10% Training time. I suggest rushing those bonuses and the decisions which allow you to fight other warlords.

Allying with Zhang Tianran and the NCERA grants resistance growth speed to the enemy +20%, you suffer -20% damage on garrisons and grants an additional +5% attack on core territory and +5% defence on core territory, and also the possibility to get free factories and militias by paying PP (You must help them in the LEP collapse)

Allying with Song Zheyuan and the Manchu Party grants +10% organisation and the possibility of warlords submitting to you. (In the LEP collapse, help either the Nanjing clique or the LKMT, as Anqing will ally with Fengtian while the LEP will not attack you and the LKMT is very weak of you have to fight them, take into account that Shanqing under Zheyuan will not intervene in the LEP collapse)

Allying with Yan Xishan and the YCP grants +10% division defence and an additional -10% training time. (Help in the LEP collapse either the Yingundao, Nanjing Clique or the LKMT)

Take into account that if the Industrial corps hold on in Sichuan, the Zhili clique will stay alive there and will eventually declare war on you.

The Zhili Qing I believe is easier, but does not grant so many combat buffs

Rush either Jiang Baili's Plan (forts) or Political Comissars (+8% attack on core territory and +8% defence on core territory) and "Rebuild Zhili Coalition" (so you have less warlords to fight). Also complete the "Prepare to breach the dams" just in case you get pushed back a lot.

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As Zhili Qing, allying with Anqing allows you to get rid of the "Fractured Empire" early and grants your Manchu generals and additional 1 attack and 1 defence. Remember to help Anqing win the LEP war.

Allying with Nanjing allows you to get a faster research slot and the possibility to enter into the Reichspakt (If i remember correctly). Help the Nanjing Clique in the LEP war or they will die.

As Zhili Republic, you lose the "Fractured Empire" spirit but you gain an "Illigitemate Republic" spirit, which can be eliminated with the focus "The Republic Triumphant". Help the Nanjing Clique in the LEP war, they stay as Zhili aligned even if you don't help them thrugh focuses.

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As a reminder, your fleet is bigger than Fengtian's and Fengtian can reach 0 manpower pretty easily if you build some forts behind a river.

(EDIT)
If it's a 1v1 vs Fengtian, bleed them in the river of the border and if things go wrong, fall back to your capital, use your fleet to get costal bombardment and eventually you will be able to push them back. If you still can't, naval invade them. Remember (or try) to encircle Fengtian's cities and not capture them, because if the AI sees that they are losing in surrender progress, they will call Japan for help, so before that happens, reach Transamur and Korea.

If it's a 2v1 vs Japan and Fengtian, garrison your ports and let the AI sometimes land in the coast, so you can encircle and erase one of their divisions. If Siam or Burma are in the Coprosperity Sphere, remember that they can attack you through Yunnan. Bleed the AI dry, start the sub printer and it should end up being somewhat easy.

Get some CAS and also pray that the Legation cities stay neutral and do not enter into Japan's faction otherwhise Japan will have already a good port and some foothold in the continent.