Remove Google Apps mini and install another version - LineageOS I have installed LineageOS 14.1 (+TWRP) on Samsung S5 g900f (klte) with Google Apps mini. I followed this guide: 
https://wiki.lineageos.org/devices/klte/install

I also added Google Apps Mini zip during the installation phase.

Question:
Is there a way to remove Google Apps mini and install Google Apps nano (or pico) package? (Without reinstalling from scratch)

Regards
Flashing the LOS package again (to restore /system to a clean state) then flashing the GAPPS you need should be sufficient - no need to do a factory reset. Of course, do a nandroid backup as always just to be safe.