Which would be better load wise on the hubitat, or are they fundamentally the same
A Rule that is triggered on system start that has an action that runs every few minutes (with the interval being set by a delay), or, just a rule with a trigger every few minutes?
Thoughts?
Neither is probably great and I'd be interested in what you're doing and why, but both sound about the same to me. 
The end result of each would be a scheduled job that runs at the specified time, waking the Rule/app up when needed--it won't be "running" while it's waiting for the next repeat, schedule, etc., if that is your concern. Apps in general pretty much just wake up, do their thing, and then wake up if/when something wakes them again. These are just two different ways of creating those schedules.
That being said, second option sounds both easier to set up and possibly more reliable to me (no schedule "chain," just one job scheduled with a cron string).
Now, I didn't actually say I would be writing an actual rule to do this. 
This was just more of a paper exercise in my mind to try to understand a little more under the hood on how the hubitat handles jobs like these. I had pretty much come to the same conclusion that you did, but wanted to know if I was missing something.
I'll admit it. I'm OCD when it comes to optimizing things like this. I'll optimize till it breaks. 
Download the Hubitat app
