@burialchoice The very very most important thing is developing a lifelong habit. The seniors in my old yoga class all stay very active - biking, walking, yoga, golf, weights. Doing anything consistently is the most important.
Flexibility and later balance is super important. Yoga is great for keeping your range of motion, balance and helping with joint pain. And working on posture will help you keep from developing little-old-lady hump. And it will also pair well with...
Strength training. Like you said about muscle loss, but also helps reduce bone loss as you get older. And it can also help with stability depending on what you're doing.
And the cardio that you have covered.
You don't have to go super hardcore with any of these. I'm in my early 40s, and run 3 days a week, so strength training 2x a week for 30 min, and yoga 3-4 times a week - currently just some videos off the internet, but I'll probably be going back to in-person classes soon. My mom in her 60's does strength training 2x a week for an hour, and does a lot of walking on the treadmill, and does archery/other target sports a few times a week.