Can you give some more info about that, especially with a smart trainer? I would like to give this a go, and I'm still debating whether or not to get a new trainer, to replace this old manual thing (that you can't change resistance on the fly easily on)... so stuck with gears and it just feels ... wrong.
No probs.
The smart trainer basically removes your need to worry about adjusting the resistance manually. On actual workouts you create in Zwift, you specify the time of the effort and the recovery time. You then set the watts you want to hold for that effort and also the cadence and the smart trainer then auto adjusts resistance as you perform the effort to keep you at that specified watts/RPM (this is ERG mode).
Zwift allows you to create custom workouts. During which you can setup warmup and cooldown periods and you can setup intervals in between those to whatever you want. 10min warmup - 10x1min efforts - 20min cooldown OR 30min warmup - 2x30mins - 30min cooldown..... anything you want. For every aspect of this you can specify max/min watts, RPM etc and the ERG mode keeps you in line with all the figures you specify without you needing to change gear at all manually on the bike.
If you jump on Zwift and just want to ride the course without doing a workout you just pair your smart trainer as normal, jump in and it will toughen up resistance and reduce resistance in the trainer as you come to climbs and downhills etc. At this point you will use your gears manually on the bike just like you would outside as you come to climbs and downhills.
You can though, change it, so that Zwift isn't using your smart trainer over the FEC ANT+ standard (which allows it to control it). In this case you could pair the trainer and just essentially use it as a standard trainer but still get power/RPM/speed readings but it won't change resistance for you as you get to climbs or downhills. In this case you could control resistance yourself with your gears on the bike or you could use the app for that specific trainer... in my case the Wahoo Fitness app which allows you to control resistance in a few ways such as using ERG mode as mentioned above, but manually, so you can set the phone app to 300w any moment you want and the resistance will control this for you.... Can also use a different more traditional method of control using levels 1-9 where it gets harder as you up the levels etc.
So yeah, hope that explains it well enough, but with a smart trainer you basically maintain the ability to use it as a traditional trainer with the benefit of having a power/cadence/speed sensor built in but you can more importantly use it over FEC ANT+ so that applications like Zwift/TrainerRoad can control resistance for you as you train. The top end like Neo and Kickr really cover all basis and integrate with any which way you want to train indoors.
.
