BEDS and PLANTERS might have different requirements so can't be lumped together as one solution fits all. Why are you installing these drains in beds? What makes it necessary? (A picture might be helpful.)

The backyard is raised higher than the patio, and the slope runs from the back wall down towards the patio seating wall back. In order to prevent rainwater from overflowing onto the seats, I have surface drains in the beds above the seating wall.

"... and the slope runs from the back wall down towards the patio seating wall back." Sorry, but that does not bring a clear picture to my mind of what is happening. You've seen it so you don't need a picture, but I don't even know if the word "back" is a noun or adverb.

Is there any reason the pitch of the bed surface could not be directed so as to prevent rainwater from overflowing onto the seats?

Hi, thank you for trying to help.
I'm adding a couple pictures to try and help you visualize.

I was running out of time and I had the contractors run the drain pipes to the front sides of the planters and flower beds.

Where front is the part closest to where you would be standing.

Does not matter how the back is graded, the water will flow to the front of the house, as the house is on a slight incline, and flanked by concrete walls.
I am trying to prevent the water from running over the seating area and leaving debris and stains.

Images coming in next post.

Pic

East wall planter

West wall planter

It looks like you've got a serious project in progress. It sounds like you're only trying to determine where best to CATCH the water (?) ... regardless of how the drainage paths will be routed. I think it would be best to take into account the overall drainage plan in determining where the catch basins will be located. Even with the pictures, there is not enough information provided to determine how you could best be helped. Drainage should have been worked out as part of the design of the project. It sounds as if, now, you've taken your best shot and it will either be adequate, or it won't. If you want to pursue it further, you would probably need to provide basic grading and drainage information on a plan, even if it's a simple sketch.