The custom configuration is nice IF you know exactly what you want, and it is overwhelming if you don't.

The Ribble summer deal on the Evo Pro Carbon for £999 is a spectacular deal, and all decisions made. Look for reviews on it, and you will find much positive press.

Gearing is very personal. A standard crankset is 53/39, a compact is 50/34. IMO, the only significant difference is the 16 tooth jump of a compact doesn't shift as smoothly as the 14 tooth standard. You may get easier gears with a compact, you may not.

The cassette numbers are smallest and biggest cogs, so think hardest and easiest effort. Wider may look better on paper, but the larger # spread means bigger gaps each time you shift. So a 12-25 makes a nice pairing with either crank. An 11-25 does as well, but means you will lose a gear in the middle, as both sets only have 10 cogs.