You can't really put lighting in the beams themselves. You could add some cross beams that have room for wiring and lights. It depends what youre trying to achieve. Small molding would be better.

I would not put any lighting on the timber beams. They are even lower to your head, do not work with a proper lighting layout, and would be like attaching a barstool to the fender of your car.

Lighting can be designed for the function of the rooms, attached to the ceiling planks if needed, and you have some choices depending on your goals. Molding can be used to partially hide cabling, but the reasons for the molding and how extensive you envision it should be understood too.

Do not cut holes in those beams without an engineer. Even if they are decorative they may need the strength to hold themselves up.