Take a look at the attached graph. Both per second recording. Same run. One is current pace from my 945 with GPS + GLONASS (displayed as speed in kph here) and the other from a Stryd foot pod with Speed=Always so taken from it.
The one that is a lot smoother may not be the one you think it might be :)
Looking at other runs on my 945 they also display similar smoothness. Do your runs if you have one yet?
Conclusion if you want a nice smooth current pace, the 945 without any "accessories" may well do you. ciq.forums.garmin.com/.../1480359.png