As an older guy myself, my thinking is that your goal of riding 50 miles is a good one, and actually fairly modest, so I'd say mostly what you need is miles under your belt, whether virtual or real. I'd suggest a combination of both. At the moment, I'm riding during the week on Zwift, and on the weekends on the road, weather permitting.

I've been riding for most of the last 25 years, but with some fairly significant gaps, so I know a bit about building back up. When I've had a layoff of any length, I generally start up with 16 mile rides on a mostly rolling road that's nearby. That makes for a nice, hour plus ride. I can take it at any pace that's comfortable, and it gets the legs used to spinning again. Then I start adding miles onto that, and some more climbing as well - gently, and using all the gears I have. Over a couple weeks to a month I'm back up to 30+ miles on a weekend ride, and just build from there. I ride a couple times midweek and a long ride on the weekend. This is what I've been doing in Spring most years recently, because I've found it hard to ride the trainer.

I find it REALLY HARD to just spin a trainer for more than about 20 minutes without losing focus, so I have to play loud music with a fast beat to keep going - like the B52s (See? I said I was an older guy), and then I can make it to 45 minutes. I started riding on Zwift back in August, when the fires in Northern California were making the air outside unhealthy for exercising, and it makes it possible for me to go over an hour without boredom. It's not as good for the soul as a ride on the road, but it's better than no ride at all. There are structured workouts but I don't know that you need them unless your goals become more ambitious. Just ride. Get on Zwift and spin around the various worlds. Chase down other riders. Throw in a sprint or a climb every so often.

Regarding weight loss, I've lost almost 30 lbs this year myself. For me, it's all about calorie counting, because without it I'll overestimate how much food I need to compensate for what I burned on the bike, and end up at the same weight. But that's me.