If whatever wearable you have can upload a graphic ECG representation that you and a professional can read, it will show a proper depiction of a PQRST wave complex and you can see, for yourself if educated about reading them, what kind of problem is depicted. Atrial fibrillation shows no discernible P-wave, and the R-to-R peaks are all over the place in terms of distance/time between them...no reliable pattern. If PACs, you can see the close couplets or triplets, followed by an obvious long pause, and then the catch-up beat. https://en.wikipedia.org/wiki/Premature_atrial_contraction
The wearables aren't licensed or certified to do more than to report AF, which along with VF, are the two most problematic or concerning arrhythmias, with the latter being potentially lethal inside of a few minutes. But if you take pains to learn how to read an ECG, you will soon learn what AF looks like and when you have PACs with bigeminy, trigeminy, or even bundle branch block if your wearable has the accuracy in the one lead to detect it....which pretty much none do. In fact, most pros will tell you that a 12 lead ECG is what works best to show clearly what is going on in the heart's rhythm.