Don't be afraid of bike computers that do all that nifty stuff. You don't have to use any of it. All of them do the basic stuff very well. One thing Garmin has going for it is that all the Garmin devices I've owned in my lifetime still work. About 20 of them all together. With the exception of a Marine Chart plotter that spent two weeks underwater after my boat sunk in Hurricane Katrina. It got a little bit of water in it. Even so, it continued to work for 2 years after we got the boat off the bottom and cleaned everything up.

Just decide how much you wish to spend on a bike computer.