What is the best CPU for Fortnite? Will an AMD RYZEN 5 2600X fit? And does the graphics card fit as NVDIA GEFORCE GTX 1660?
Yes and yes.
9100 +1650 great
The AMD Ryzen 5 2600 or the Ryzen 5 1600 AF (both almost the same processor) are well suited for Fornite. The GTX 1660 fits well as a graphics card.