If the Amiga dictate the clockrate it will be cycle exact, because the Amiga defines it.
And most TV sets use HDMI, better get started with it. Or the video output options might be as limited as trying to read 5,25" floppys.
simpler get a TV with SCART, or convert RGB to YPbPr (think EAB has such project).
iirc, the HDMI thing wouldn't work because Amiga does D/A conversion inside a chip.
so you'd need to do a A/D conversion for HDMI, and that sux, and most TVs can do that with component signal already.