^Great info, Sabroso. In order to avoid the lag and benefit from the increased compatibility, you could send the OSSC output to a HDMI splitter. One output of the splitter to the TV, and one output to Xbox One->capture card.
^^Kenzya, is your SCART cable csync or sync on composite video? If sync on composite video, I recently learned (thank you marqs) that the H-PLL Pre- and Post-Coast settings can help compatibility. If it is csync, have you done the dejitter mod?