Pocket Operator set up, seeking connectivity help

I’ve been having a lot of fun with pocket operators and these korg mini synths over the last couple months. I’ve built myself a portable rig to connect to a bluetooth speaker (thru aux input) or a guitar amp, but I seem to be experiencing some issues with the connectors/cables that I have and tried.
If possible, I’d like to run two signal chains;
Line1: PO32 (SY1) + PO33 (SY4)
Line2: PO28 + Duo + Delay
Note: I only want the Delay on the PO28 + Duo. I don’t want the PO32 + PO33 to go thru the Delay.

Before I explain any more, what would be the best way to achieve this? What connectors and sync modes should be used?

Is there a way that i can connect everything in one line BUT only have the PO28 going through the duo and delay. I don’t want the PO32 or PO33 going through the duo and delay.

I have a bunch of TRS connectors and a few Y splitters, but I get different volume results for each gadget through all the connections that I’ve tried. I’m well aware of how to check volumes on pocket operators; that is not an issue. I even tried a headphone amp at the end.

Two of my Y splitters sound similar but I have a third splitter significantly lower output or atleast one side seems to be a lot lower than the other.

I feel like there might be a better solution. Also considering incorporating a Maker Hart Just Mixer if that might help but I’ve read mixed reviews on it.

Any help is appreciated.

Thank you.