The greatest risk is from stroke. When you are fibrillating, the LAA does not get properly 'washed out' or flushed with each beat, and that is where they find the clots originate. The risk rises with frequency and duration, so if you have a short run, ten minutes, and then nothing for weeks, you can probably cease the DOAC.......ON THE ADVICE of your cardiologist. I would ask you not to do this on your own accord, but with agreement from an expert. Remember that one's risk of a stroke is not solely reliant on whether or not you are fibrillating. There are other natural risks that we all have, and they build with age. If you have even one more comorbidity, it might be much better if you just lump it and take the DOAC....as prescribed.
Metoprolol is another beast entirely. It is a 'rate control' medication, a beta-blocker (beta adrenergic agonist). It can both slow the heart's rate, but also reduce the force of each contraction. This means it can also be used as a first blood pressure drug....as my cardiologist explained to me. In my case, I was also prescribed a statin, and that is what I blamed when I became lethargic, or had more difficulty sustaining a run. I'd had to run/walk.
I don't know about gastric problems. What problems? Repeating? Acidic or frequent belching? Acid reflux?