Any Scott foil owners out there

I've found it useful to go back over previous bike frame history and compare stack and reach. If you've had a variety of bikes you'll quickly see a pattern of fit and comfort and be able to see what works what's likely to work.

For the foil Xl is pretty much a 58 and l is a 56. I know lads smaller than you buying the xl, so probably the better size . However the foil is an aero bike so a size down would take advantage of that as you can achieve a lower position and longer (suits a more flexible rider) if you change stem length, a long stem feels nice on a road bike anyway imo.
As mentioned above comparing geo charts with your current bike is probably the best thing to do. Or getting a pre purchase bike fit, also trying both sizes if anyway possible now is what usally would have been advised pre covid.