As Tammy7 said, we vary too much to make general recommendations. Some PWME can do fairly extreme bodybuilding, while others can't walk to the bathroom without triggering PEM. We mostly have to self-experiment to see what works--and doesn't work--for us as individuals. I can do a fair level of fitness activities: walking, digging soil, sawing firewood (by hand or chainsaw) and splitting it, without consequences. I have plenty of days when I don't feel like it (lethargic, achy), but I could if I had to.
I'm less convinced of the value of extra exercise. I usually do a 2.5 km walk daily. At times, I've done that 3x a day, and added in arm exercises (lifting a heavy walkingstick in different ways to exercise different muscle groups). I never noticed any extra benefits from those extra exercises, which doesn't encourage me to do extra.
I think an important aspect of exercise is how much you are willing to do it. Some exercise machine might claim to provide maximum benefits, but if you hate boring repetitions indoors, you'll avoid using it. If you like going for walks, you might do that even if you are having a bad day. For me, digging soil is a good choice, since I need to fill ruts in my driveway, so this activity rewards me with satisfaction (the ruts get filled). If someone really enjoys baking bread, kneading by hand (and giving the excess to friends) might be a better choice than a membership at a fitness center that they hate going to.
If you need arm exercises, you could try carrying a walking stick or whatever, and lifting it in different ways (side, front, etc) to work different muscle groups. If you're using that time for walking, you may as well use that time for your arms too.