Ok, first of all if you had read through any threads about ROMs based on Android 9 and up, you would see that the repartitioning process is mandatory in case you want to flash any gapps package (yes, even pico). The error you get is because the stock system size of our device is around 1GB, which is not enough for the more recent Android versions ROMs + Gapps to fit. With LOS 16, you will get the same results / errors. Therefore, repartioning is the way to go.
An alternative would be to flash an an older Android version ROM which does not take as much space. In this case I would recommend razorloves's unofficial LOS 14.1 builds which are based on Nougat and ROM is still being maintained.
So long story short, up to Oreo, you are fine with stock partition. Pie and up, you need repartition!