Throwing my 2 cents in the as well.

My wife gave me a Tacx Flow Smart as an early Christmas and Anniversary gift; I had been struggling with training with the lack of evening light. It's honestly a good, cost effective way to get into Zwift, SufferFest and TrainerRoad. You have to think about what you intend to use the trainer for if you're considering a wheel on vs. direct drive.

I'd say if you're serious about training and want the best experience, spend the money on a direct drive. If you're going to be more casual and realistically looking to spend most of your time enjoying Zwift group rides, the wheel on will be fine. The Tacx Flow is limited to 800w and a 6% grade so high intensity workouts and sprints will over power it. There is also a delay when in ERG mode as it changes resistance. I'm using a 4iiii power meter in conjunction with it and makes a better experience than relying on the trainer's calculated power.