You want them along the perimeter of the cabinets, about 12-14" from the cabinet doors. Furthermore, you want the recessed lights to be equally distanced from each other.

You also want two layers of lights - so the ceiling cans, and also the undercabinet lights you mentioned. Those UCL strips need to be installed toward the front of the upper cabinets. Don't let them install the strips toward the back of the upper cabinets (it's easier to do that, saves them 15 minutes, so that's why they want to). If the undercabinet lighting strips are installed toward the back, they mostly light the backsplash. Installed toward the front of the upper cabinets, they shed light onto the center of the counter where they're supposed to.

Make sure all lights are on on dimmers, including the undercabinet lights. Dimmers are not expensive, so this is not a big deal.

Make sure the switch for the undercabinet lights are in the backsplash at easy reach. You will want to turn them on while you are working at the counter, so you'll want the switch within easy reach, not having to walk over somewhere to turn on the undercabinet lights.