Are stronger reads an advantage in playing a clarinet and saxophone? If so, how? I usually play with a 2 1/2 strength
Yes and no.
First and foremost, the reed should match your jaw strength and stamina; if you can't bite down hard enough on the reed to compress it against the mouthpiece (and then sustain that jaw pressure over time), you'll squeak. Conversely, if you bite down too hard, you'll "pinch off" the sound; it will trend sharp and then in the extreme you'll fail to make a sound altogether.
There are construction differences inherent in a 2 1/2 compared to a 3 or 4; the reed's tip is left thicker by the planing process as the numbers go up. This increase in thickness creates a more substantial fundamental tone as there's more mass vibrating to create the sound. Therefore in the long-term, reed tutors will encourage their students to work up toward thicker reeds, and this will naturally happen as the student gains jaw strength and stamina through practice. A 3 1/2 or 4 is usually the goal for school-age players to work up to, with most manufacturers making reeds as stiff as a 5. Understand that not all reeds are created equal; a Mitchell Lurie 3.5 is not a Rico 3.5 which is not a Vandoren 3.5. Also understand that using a stiffer reed does not automatically make you a better player; a Strength 5 reed is like a "Tour Stiff" golf club, only the very strongest players need one, and a lot of the greatest players never bothered.
As you practice and develop your technique, your jaw will get stronger, and you'll naturally start unintentionally pinching off that 2 1/2 reed. When that time comes, don't slacken your embouchure; increase your reed stiffness up to a 3 or 3.5. Don't try to move up more than one full strength rating at a time, especially after you've made your first jump from the "beginner" 2-2.5 strengths. Lastly, understand that the majority of the reeds you will buy in your career will be worthless; you'll buy a box of 10, all meeting the manufacturer's strictest measurement tolerances, and of those you'll find one, maybe two that are "performance worthy", which you'll treat like gold, another two or three that are "practice worthy" and will get the majority of your play hours, and the rest of the box will have some variation of material strength, shaping or other "defect" that will render it more or less unplayable.