And so, before looking at the technical detail of what can be specified, it's strongly suggested that you read some of those essays on web design, and reach your own conclusions as to the strengths and weaknesses of the medium, and how you can best exploit the strengths in a web environment, without falling foul of the weaknesses. Other people may find your choice of font size uncomfortable. A surprisingly large number of people have vision problems and require larger text than the average. Other people have good eyesight and prefer the advantage of more text on the screen that a smaller font size allows. What is comfortable to you on your system may be uncomfortable to someone else.
Browsers have a default size for fonts.
If a user finds this inappropriate, they can change it to something they prefer. You can never assume that your choice is better for them. So, leave the font size alone for the majority of your text. Remember, if people find your text uncomfortable, they will not bother struggling with your web site. Never put any of these generic font names in quotes.