F4 uses a modified version of the Creation Engine, originally designed for Skyrim. CE is in turn developed from some of the Gamebryo engine originally implemented for Morrowind in '03 and progressively upgraded until FNV in '10. The most important change is that CE is a 64 bit Engine, meaning it can take advantage of all available system resources. Unfortunately, Bethesda doesn't seem to be in the habit of proofreading their scripting or making sure that it all makes sense because their games seem to crash when scripts get jumbled. If F4's CE and Skryim's aren't terribly dissimilar, then it's likely it will support the same amount of mods.
We have arrived, and it is now that we perform our charge.
In fealty of the God Emperor (our undying lord) and by the grace of the Golden Throne,
I declare Exterminatus on the Imperial world of Typhon Primaris.
I hereby sign the death warrant of an entire world, and consign a million souls to oblivion.
May Imperial justice account in all balance
The Emperor protects.
-- Task force of the Ordo Malleus, immediately before carrying out Exterminatus on Typhon Primaris.
Thought for the day: It is better to die for the Emperor than to live for yourself.