We do not disclose or commit to using a particular LED on those, but you can look at something like Digi-Key parts 754-1578-1-ND and VSMB10940CT-ND to get an idea. But none of that stuff you asked for really matters. You can see from the sensor datasheet that the peak sensitivity is to about 950nm, so you should get LEDs that emit around that wavelength, and beyond that, just play around with them. You can see from the schematic that the front and side LEDs are in series (except for the bit of current through the red LEDs), and the idea is to pulse the current well past any continuous ratings on the LEDs, anyway. You probably want to use through-hole LEDs so you can play with the angles and shielding more. Just getting brighter isn't necessarily going to do that much for you unless you prevent excessive reflections from within your robot.