For intersections, I have usually used the hovering hand, but I get that it's not ideal always.
The splitter funnel has a soft split mode, so it sends items to whichever output has space. You can make a splitter with 2 filters by using 2 filter funnels funneling from the same location.
I don't think conveyors need curves, as you can just have one belt face into the next.
You can see source and target coordinates for structures by shift hovering over them.
The oases give a random crop each time, so in the worst case, you can farm the same oasis until you get all the crops