Running LG UltraFine 5k with additional low DPI screens
As mentioned by in the 2018 MacBook Pro 13-inch spec, this is not possible. It supports at maximum of 2 external screens:

Video Support
Simultaneously supports full native resolution on the built-in display at millions of colors and:

One display with 5120-by-2880 resolution at 60Hz at over a billion colors
Up to two displays with 4096-by-2304 resolution at 60Hz at millions of colors
Up to two displays with 3840-by-2160 resolution at 60Hz at over a billion colors