for the Stand use the most sturdy filament you have. PETG, Polymax or Nylon will work fine. PLA or TPU won't support the heavy XL.
the mudguard extender needs to be printed with TPU. it is experimental and i haven't tested it much as all the snow and mud is gone ... so i don't really know if it helps and i don't plan to improve on it much further as i only have a 12x12cm buildplate atm. feel free to enlongate it down to the bottom of the fender.
both can be used with the original screws.