Does the Spray Bar in a planted tank need to be underwater or above water?

Under water or you will outgas all your co2

If you are injecting CO2, you definitely want it underwater.
Water splashing, and surface turbulence will promote gas exchange, Not something you want if you are working to put CO2 into the water.

So just under the water line is fine? And Should i face the spray bar holes goin straight down?

point it anyway but up.
i have mine about 3" down, facing forwrd so that there are some small, light, gentle (have I made it clear that it's gentle) ripples

Under or Above

I am an underwater guy.. I do CO2.
I use a upsize tube 1/2 to 3/4 to bring the final output under low pressure at a 45 degree across the front, which creates a circular movement.
Besides that I don't like the water spots from splashing.

mine is downward at about a 40 degree angle from the water surface. Some people have their parallel to the water surface. I used to.. but I moved my plants around and had dead spots (no water moving) in my tank. I wanted to make sure the CO2 got around... so I slanted my water outlet holes to make the water move around more and eliminate the 'dead' spots.
Play with your until you like it. There are no hard and fast rules about what is best. Each tank is different.

I actually have mine spraying towards the back of the tank and down.This works out great for me because I can leave my filter on full blast and not blow the fish and plants around plus co2 is not being outgassed.

i have two. One on each end of the tank pointing in towards each other. This way the water tends to circulate better IMHO

agree

See, I knew we could reach a conclusion. I think the point is - depends. I seen many responses which I too have used in the past, but my current set up seems to work, as theirs for each responder.

good luck.

I went with the power jet nozzle it has better flow rate.

I don't use one at all anymore. I just have a 90* elbow on each of the returns, point up just enough to keep from getting surface film.

Tommy