So, a cog isn't a cog.

Is there an accepted "if you choose the cog from a cassette with a larger jump and put it on a smaller jump cassette you'll be fine"?

I'm looking to try some stuff but before I cut a new chain to size and put it on and size it for the largest cog (1x) want to make sure I get this right.

I have a 19f cog going to 20c in one cassette and a 18c to 20a in the other. Will the 20a be OK going into the cassette that used to have the 20c? The 20a allows a larger jump of 2 teeth in the once cassette so sounds fine.

Thanks.