How to Design a Balanced Workout Plan

Hi, I used Fitness Blender's stretching videos consistently about four years ago. I am just now getting back into it. I want to design a workout plan that includes strength as well as flexibility. I have scoliosis and rods in my spine, so I avoid crunches, flies, and anything that will be hard on my back. But I really want to build strength. I do not need to lose weight, it is just for my general health. My goal is to do a short workout (20 minutes or less) before work 5 days a week. What combination of free videos do you all recommend to ensure I get a healthy, balanced routine? Thank you in advance for any advice! Nicole