it really depends on what software and what personal style a person is going for so methods will be pretty different
personally i use medibang paint pro. while the software itself has a "materials" option which includes speech bubbles i tend to use the line tool or shape tool the make any speech bubbles. The "tail" of the bubbles i usually just hand draw with the pen brush.
i know clip studio paint has speech bubble assets, as far as i can recall, and photoshop had the default speech and though bubbles in cs5 or cs6 as for more recent versions i'm not to sure
to give some samples of speech bubbles i've done:
this episode used photoshop's shape tool, angled brush for the "tail" and the stroke effect to create the outline
versus this episode where i used medibang's shape tool, the draw selection border tool(effect?) to outline text that feel out of the shape, and a marker brush I "copied" from firealpaca to do the connecting lines and "tails" for the speech bubbles
like i'd mentioned before there's a ton of different methods it's just a matter of finding what works best with your artwork/artstyle, what your style preference is for speech bubbles and just finding methods that your most comfortable with or are the most effective. it takes some experimentation but it pays off and you get to learn a variety of methods to use/shortcuts you can take
sorry if my explanations are disorganized but i hope it helps