Nissin i40 or Sony hvl-f32m flash for Rokinon 12mm manual lens on Sony a6000

[mikej411]

I am looking for an external (speed light I think its called?) flash for my Sony a6000. The reason I am looking for an external one is because I just purchased a Rokinon 12mm manual lens. This lens is nice and compact, however, it sticks out far enough to block light in the bottom left portion of the picture when using the built-in flash on the Sony a6000.

I read a little about both the Nissin i40 and Sony hvl-f32m, and they seem to be what i'm looking for in terms of performance, price, and size. I want TTL for sure as im a beginner and wouldnt know how to manually set the flash. I dont the external flash to be wireless, even though these ones are. I like the compactness of the Nissin i40. I believe the Sony is a little bigger, but not by much? Keep in mind I have read only very little about using external flashes, so feel free to suggest similar but better options. I believe the posts that I read about these flashes were years old.

My main question is geared towards the compatibility with my Rokinon 12mm. I noticed when comparing the two external flashes Compare Nissin I40 vs Sony HVL-F32M vs Sony HVL-F43M vs Sony HVL-F20M), that it says this

Angle of coverage:

"Nissin i40: N/A"

"Sony: 84° - 23.3°. Wide-Angle Adapter: 110°"

Coverage:

"Nissin i40: 24 mm - 105 mm (Full frame)"

"Sony: 15 mm - 105 mm (Full frame)"

Note that the Nisson's lowest focal length coverage is 24mm. My Rokinon lens is at 18mm. What exactly does this "Coverage" mean? Will this be a problem only being 24mm at the lowest? How will it affect my pictures?

Also, are these good external flashes in general? Any other comparable ones that are cheaper? Or any newer/better ones at that price point and size?