Thanks for your answers pushbrk and Mike E. I have a few more questions *facepalm*
1. Is proof of employment needed for form I-864? The form instructions don't mention it but it says here under 'How to File an Affidavit of Support' it is needed: https://www.uscis.gov/green-card/green-card-processes-and-procedures/affidavit-of-support
2. Is the ID card (Shen Fen Zheng) one of the required civil documents? I just hadn't seen it mentioned before. It's listed on the Civil Documents by Country page, but it's not listed in the Guangzhou consulate page listing required documents: https://travel.state.gov/content/travel/en/us-visas/Visa-Reciprocity-and-Civil-Documents-by-Country/China.html
3. My wife's English name is April, she's never used it on anything official, but my family know her as April. It could be considered a nickname. Do we need to add it to DS-260? And if so do we need a certified alias certificate as mentioned under Pre-Interview Checklist -> Birth Certificate here: https://travel.state.gov/content/travel/en/us-visas/Supplements/Supplements_by_Post/GUZ-Guangzhou.html
4. The full course of the covid vaccine must be completed before the interview (this can be found under Medical Exam in the Guangzhou link above), so would there be an issue with getting the covid vaccine on our own now, and keeping the documentation to bring to the medical exam? And if so, does the proof of vaccine need an English translation? She doesn't have a record of any vaccinations, so she'll need to get all the others at the exam.