Why does my furnace have different startup sounds after maintenance?
Disclaimer: I am not a HVAC technician, and this is speculation on very little information.

I am guessing that what you describe as “like an amplified version of burners flames on a stove” is mostly the sound of the gas flowing through the piping and burners, not the combustion itself.

The “big whoosh”, then, is when the not-yet-burning gas reaches the igniter, and a bunch of gas ignites all at once (causing a noise as the gas and air becomes very much hotter and expands).

If there is less “big whoosh” but the furnace is doing its heating job, that suggests that the gas is igniting more promptly with less accumulation of unburned gas, which is, all else being equal, a good thing.

I would suggest that to further settle your mind you should look at the flames. They should be blue (with perhaps occasional orange flickers but not continuous ones) and in a neat row, and when they ignite they should not spill back out of the burner and heat exchanger area even for an instant. Don't remove anything other than the usual outer access panels to get a look, as it might change the airflow away from normal.