I think in most cases you mean that the effect buttons can be too large at times (not the icon). This being because the text in the button makes it larger rather than the icon.
I do think the icons do provide some information about what the effect does, but not all the necessary information and neither does the name. The effect buttons already shows a hover tooltip that is the segment effect name, so if we want to enforce equal size segment editor effect buttons by way of equal size icons with no text shown below, then that could be possible. Other applications with various tools for image annotating, usually use an icon only, with the hover tooltip detailing both the name of the effect and also a short description of the tool. The addition of a short description in the tooltip could help if the text was removed from the segment effect button.
Note that this actually happens not due to the effect button size, but rather the effect options. A specific effect options can be larger in width than others which causes the module panel to increase when it is selected. I’m not addressing that in this PR, but that is another issue that was brought up for general segment editor improvements.