There is a person that goes by the user name Morris posting on another site that uses this very combination to get really good wildlife images. He explains his setup here:
https://www.fredmiranda.com/forum/topic/1772910
p.s. Welcome to the forum.
p.p.s. This might interest you as well:
https://www.fujirumors.com/sigma-23mm-f-1-4-and-sigma-100-400mm-f5-0-6-3-for-fujifilm-x-officially-announced-reviews-and-pre-orders/