Thanks :)
I try to provide choice whenever possible. Technically, yes it is a bit more advantageous financially short term to have sales on itch. On the other hand, more steam sales = more validated reviews = more views = more sales. Point is, do what's best for you, there's pro and cons to both options from my point of view :)
Note that guides and mods are available on the steam community & workshop pages. Those are not available here, as itch.io has no such infrastructure. You can still use the steam key and with a bit of elbow grease move the mods to the non steam version. Ofc, you can read the guides from the steam community website directly.
Cheers, and thanks for your purchase.