if it is relevant I have a rain screen assembly, w/ 3/4” thick plywood as my furring strips w/ Tyvek house wrap. And this is probably relevant too – I did make a way for the rain screen to vent out at the bottom of the window

On the vertical portion of the right side of the window, what you see there in one of the pictures is what jeldwen calls a mull groove filler, it’s a strip of vinyl that snaps into the groove that runs all the way around the window. Presumably this makes it easy to attach jeldwen custom trim; just snaps in place. My dilemma is this – do I even use those mill groove fillers, do I caulk the groove instead… of I don’t caulk but opt for the groove filler this is time consuming (not easy to install) and doesn’t seem waterproof anyways)  and I’m asking because without anything filling that groove, as you can see there’s almost no ‘meat’ for the caulk to stick to.

the bottom horizontal portion of the window does not have anything installed in the groove as you can see, as it would cover the week hole, I tried installing a strip while drilling a hole wherever the weep hole was, and it just didn’t drain that well as it gets trapped behind the mill groove filler strip.

a) what should I do with the vertical joints?
b) what should be done about the weep hole/bottom joint?and is caulking the bottom of window trim even necessary or not ideal at all given the venting provided already? The trim is flat at the base of the window for about 1”  and then slopes down – I will try and include a good picture of this.

and sorry for any sideways pictures – some seemed right others were sideways and I couldn’t fix…

thanks for any help.