I’m not sure what you mean by H264 not support that resolution. As far as I’m aware you can encode a video using H264 to any pixel size you want.
Quicktime will only play if Windows Media Player is able to play that format. Normally you’d have to install codecs for that to happen.
Xibo has no direct support for video walls as I mentioned. You may be able to account for bezels in your Windows display settings by adding a gap between the screens there, or in your graphics card driver.
Certainly cards that are designed for that use have specific settings for bezel correction.