I’ve recently bought an Wahoo Elemnt Bolt.
Just to follow on from the comment above about required use of a smartphone – you need the smartphone to set the device up, but you do not need it with you to operate while riding; it doesn’t piggy back the GPS/data signal from your phone or anything like that.
You can use the phone on the fly though to send a new route to the device though, and it will do all the text message/call stuff that Garmins will do (I think).
One thing the Elemnt doesn’t have is bike profiles – so you can’t have road bike, hard tail, full sus profiles, for example & assign different sensors to the different bikes.
A final comment – if you shave a tiny amount of plastic of the tabs on a Garmin mount, the Elemnt will fit. I have done this to two of my Garmin mounts, so I have a mount on each bike (Wahoo one on my road bike & modified Garmin ones on both mountain bikes). And the Garmin still fits on OK, with no apparent loss in security.