i tend to start my mornings and the beginning of my workouts with yoga. especially yoga focusing on the muscle area i’m about to workout. i consider that my warm up, then for my cool down i also do a few more all around stretches/yoga poses.
It’s okay. You can do some strength reps focused on a single muscle (eg. abs, trunk, chest), or a full-body strength workout, and then a yoga workout. You could also do some HIIT or cardio like running, cycling or ellipticals and then do some yoga to cool down and get a good stretch.
I don't see why not, yoga is similar to stretching before a workout but maybe a bit more work, just make sure to not burn yourself out 🙂