What should I pay attention to in video interview?

If your Mandarin is relatively standard, they will certainly understand. I suggest you don't speak too fast, you can speak slowly, which will also leave a stable good impression on the interviewer.

How many video interviewers are there? It's really hard to say It usually takes two people, one to ask you questions and the other to take notes. I think there are at least two people.

When interviewing, because it is a video interview, you'd better dress appropriately. Don't think that video interviews can be careless about clothes. This dress must be standardized, and the hairstyle and everything should be neat.

The first video interview felt that the salary should not go up. I feel that under normal circumstances, a second interview will be arranged for you after the video interview. Maybe you should go to their company for a second interview, and it will be more appropriate to raise your salary then.