It depends a lot on the instructor. If yours rides a lot or rides competitively, that's a big help.

Generally, spin classes are structured to create 1 song intervals, so really quite short and intense. That's a good thing. You want to go as hard as you can during these intervals and not crap out before the end of the song. You want to use all the tension you can during the high tension low cadence intervals, and spin super fast with moderate tension during that type of interval. If you are just starting to go anaerobic before the end of each hard interval, that's good.

However, if you are doing 5 spin classes/week, you'll have to periodize this advice. IOW, do 1-2 classes/week as the above, and then go moderate during the other classes.

If you apply yourself during spin class, it will make a major difference out on the road. You'll still need saddle time, and might get that more effectively by using your road bike on rollers and spin class maybe only twice/week. That'll smooth up your pedalling and give you better road feel.

Using spin bikes puts you at a disadvantage because the big flywheel makes it easy to get by with an inefficient pedal stroke.