Hi yukichigali, unfortunately the Xing Hong VCD player just plain sucks.
Its playback is jerky and sound usually always goes out of synch. I have heard good things about the Dream VCD player from Lik-Sang though.
Also with the Dreamcast you will also suffer when using resolutions like 528x480, I used the Dreamcast DivX player and the same jerky problem happened unless I made my res 352 x 288 (I live in PAL country) with 22khz mono MP3 sound.
The DC cant handly large resolutions because I doesnt have enough memory to sufficiently buffer the video data and so it will lead to skipping.
So In your case its best to stick to 352 x 240 resolution, but like I say that Xing Hong VCD player is really bad I had it and the quality even with plain VCD's was aweful with jerky motion and out of synch sound.
I hope this info helps.