I have ball valves close to the tank and at the sump. Maybe should swap to hate valve for better control.

The horizontal runs were done with a gentle downslope with roughly 2-2500gph.

5000 gph??? Holy crap, which pump are you using and how big is this tank?

What's the purpose of the ball valves near the tank? Are they wide open during operation? If not, open them up and control flow at the sumo only. That alone might help.

May need to tweak that ball valve. Should clarify 2-2500 total not each drain. This is a 210 gallon tank.

Ah ok. Have you measured the flow? Or are you guesstimating? That's still a lot of flow through the sump for a 210-gallon tank - over 10x turnover. You could cut it down to one drain, do 90% total possible volume through that one alone and it'd probably be a lot quieter. 1250 gph through 1.5" drain isn't a lot of flow which gives the opportunity for air to build up and make noise. You should be able to get around 1600 gph through a single 1" herbie drain - often a lot more depending on how much restriction is on the line (such as horizontal runs slowing it down). Also, did I suggest to cut the drains so they are only 1" below surface in the sump? That will help flush air out.

Thanks for all the fantastic suggestions and help.

I am not getting good surface skimming ie film at opposite end of overflow, would it be beneficial to add an internal overflow at this point? Or just add another phead at this point and/or remove the teeth leading into the external overflow...
Thanks