You need to make sure spatial is turned on in settings

for spatial audio, you need airpods pro

You don’t.

https://support.apple.com/en-us/HT212182

so dolby atmos is the same as spatial audio?

You need to enable Dolby Atmos to be always on in the apple music settings.

I've found that Atmos has an immersive quality and I really like some of the mixes I've listened to. I usually don't like spatial effects in audio as they often sound gimmicky and unnatural, like the aural equivalent of early 3d cinema.

Yes

It’s not the same, they work in tandem on APP but you can force just the Atmos on in settings for other devices

It's all item based audio, and not panned tracks anymore. Basically the same thing