Whether we're talking land borders or airports, both are entrance points into the country where you have to pass immigration. There really is no difference and thus it IS very relevant to talk about.
Poipet is in Cambodia so your experience there isn't relevant to Thailand unless you are referring to Aranyaprathet.
Mae Sot I found less friendly about 10 years ago but they improved after around 2015 once that unfriendly immigration lady I often encountered was transferred to another location. Mae Sot is irrelevant nowadays to us farang as we can't cross there now. It's for Thais and Burmese only.
Don Muang prior to 2006 - nope, didn't strike me as being friendly. Most of the time officers would be grumpy, stamp your passport and place it down on the table with no smile, no welcome or sawatdee krab/ka.
I have encountered the occasional friendly officer at Suvarnabhumi though. In the immediate post Covid period, late August 2022, the lady immigration officer I had was a gem. Very polite and engaging.