Summing algorithm is exactly the same in (nearly) all of the DAWs. However, as soon as you start modifying audio by other means (fade in/out, automation, panning, time stretching, resampling etc) there can be subtle (mathematical) differences, depending on the algorithm implemented in the specific DAW.
AdmiralBumbleBee recently did a series of tests that show some differences between DAWs
https://www.admiralbumblebee.com/music/2019/12/08/Daw-V-Daw-Pan-Curves.html
However, most of the time these differences will be inaudible to humans or so small, that it is not worth your time.