this is what i've got in XIV although it doesn't do what you have in mind as is
you can see by adjusting Y coords you can get them onto the same line, after that, just use maxwidth to force it to a certain maximum length
[TextBanner]
TitleX=-90
TitleY=-2
TitleOnCommand=shadowlength,0;horizalign,left
SubtitleX=-90
SubtitleY=0
SubtitleOnCommand=shadowlength,0;horizalign,left
ArtistX=-90
ArtistY=0
ArtistOnCommand=shadowlength,0;horizalign,left
TwoLinesTitleCommand=zoom,1;maxwidth,195;y,-9
TwoLinesSubtitleCommand=hidden,1
TwoLinesArtistCommand=zoom,0.6;maxwidth,296;y,8
ThreeLinesTitleCommand=zoom,.8;maxwidth,240;y,-10
ThreeLinesSubtitleCommand=hidden,0;zoom,.5;maxwidt h,360
ThreeLinesArtistCommand=zoom,0.5;maxwidth,296;y,9
__________________  |