I would suggest that you get some time in on the spin bikes that you can use. Resistance bikes do not have any "momentum". They just do not have much of a bike feel to them (at least for me).
Spin bikes have a large freewheel. That produces momentum and they feel quite a bit like riding a bike on the road (again, at least for me). The other thing is they are direct drive so you pretty much have to learn how to handle a constant cadence which is a good thing. As mentioned above, working on getting your cadence up to or above 90 rpm is a good idea.
There is a problem with this. You can get into really good shape by just working out in the gym on these things. It used to be that when most people went out on a group ride, the highest speed they could sustain was about 15 mph. In other words, they were too slow to really get themselves into trouble. They learned how to ride in a group at low speeds and gradually moved upwards.
The problem with the spinning phenomenon is that one sees neophyte cyclists who can sustain speeds of 20 mph which is fast enough to get into a crash in a group ride if you make a small error in judgement. So if you go out into a group ride, be careful until you learn the ropes.
You mentioned about getting involved in semi-competitive racing. There is no such thing. Even just ordinary rides that go at high speeds can get crazy competitive. But you will probably find that one out too.
Good luck to you.