I've used a Kurt Kinetic trainer and a Kickr Snap, both with a powertap wheel.
If you don't have a smart trainer, it doesn't vary the resistance, so you don't feel the hills. You would shift into a harder gear on a hill to make the resistance harder and output more watts to try to maintain a faster speed in the game. It takes a few minutes to get used to up-shifting on a hill, but once you are used to it, it's fairly good game experience.
If you have a smart trainer, it will increase resistance for you, so you tend to find yourself shifting into a lower gear. It's a more realistic game experience.
If you can afford a smart trainer, it's a much more immersive experience, and you can use the intervals in ERG mode. If you already have a power meter, the payback is a bit less to use a smart trainer, but still was worth it for me. If you do already have a power meter, and are still looking at smart trainers, make sure if you have powertap wheel you get a wheel-on trainer, so you don't lose your actual power readings. My Snap power readings are wildly inaccurate vs my powertap, even though they claim good accuracy.
If you can't afford it, just buy a quality trainer that zwift has a power curve for. But it's worth it to buy a smart trainer if it's not going to break the bank.