What size chainrings should I get?
If you are getting spun out in high gear now, using the same gears with the shorter arms may fix this. For most riders, dropping 4 or 6 teeth on each ring seems to work well. If you currently use low gear far more often than high gear, you will want to use even smaller chainrings and/or a bigger cassette.
Most people with 26" drive wheels are going from 30-42-52 to 26-36-46 or 24-34-44. Faster riders are using 24-39-48. A few have gone to 22-34-42.
When I shorten Shimano 105s & Ultegras, about 1/3 of the owners have me install 24-39-48 FSA ramped and pinned rings to replace the stock 30-42-52 setup. Cost = $84
It's not unanimous, but a large majority of riders with 20" drive wheels and shorties do well with standard "Road Triple" gearing of 30-42-52.