I can say the LN does better then WN in story pacing, but the WN is better at the slice of life part since in the WN the author can stretch the story as much as she liked. So my suggestion is reading the LN from vol.1 till the latest. Then read the part of WN in the same part as that cliffhanger at LN. Like i read LN till vol.14 then i read the vol.11 WN. Just suggestion though if you like the story.
I had read the WN from beginning first so maybe this suggestion is wrong since i'm already aware on a lot of it's changes. This is just my opinion.
Satou gained the bell in the WN from dungeon treassure box or something in WN Vol.13. He used it fighting the green greater demon getting the demon out of Demon Lord Shin's body