Tempo is normally an effort just below what you cannot maintain for an hour. It is a exertion level.
Rhythm is better describe in my words - a groove. Just get into it and go. You can blow up, but that is what experience is about. Get a bob and weave you feel good about.
Speed is more important than effort or power. Get the grove that makes you go faster and forget about "spin", "smooth" or "straight".

The muscle groups do not put power (force) down evenly through the circle. Spinning kinda normalizes that, but few spin up hill.
In climbing, lay down the power/torque with the big muscles - Gluts, lower back, quads. Stand up, sit mix it up. As such many great climbers bob a bit. They will often not ride as straight as the slower rider.

I'm just a big guy, but been around some great climbers, both wife and son, but others who they have competed with are great and I noticed this trait.
Junior here doing a great effort (~380W/hour) you can see his bob. No PM, no attention to HR, just a groove.
https://vimeo.com/210865020