What is the optimal resolution for Sky Replacement Skies?

[Fotomaker01RA]

I shoot skies to use as my personal "stock" & add to my Ps Sky Replacement collection. 

What is the optimal resolution (aka, pixel dimensions) I should create for sky photos I want to add to Sky Replacement?

Do different dimensions affect my flexibility to expand or minimize the swapped in skies in Sky Replacement? If yes, that's why I'd like to know the best size (or minimum size) to provide the flexibility to do so and retain quality of the image.

Thx! I've done a Web search and couldn't find an answer in the Googleverse.

[D Fosse]

It will be scaled to target size. So anywhere in the vicinity of your original files.

Since the sky normally doesn't hold any significant detail, this usually isn't very critical. But in some cases you might want to keep an eye on noise structure.

[Fotomaker01RA]

Thank you. I often find that skies I load from other sources are noisy.

So, I'll be sure I clean any noise on my own sky shots before adding them. I shoot with 21 m.p. camera(s) micro 4/3. Not full frame. Not medium format. I capture Raw but save as .jpg for sky replacement Sounds like I should be okay with out of camera dimensions. 

Thx for your reply.