Not sure what you would have to use for FLV, I know you can do it in Premier Pro with an external plugin, but I can't help you there sorry.
With xsplit, change the file output to MP4, however just look around to see what programs there are and fiddle with them. This way you get a bit of understanding as well. However youtube accepts FLV files as standard so you can just reduce the recording quality on xsplit as another option.
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