I used my LG V20 a few times when I bought it, just to try it out. I forget what app I used. It worked okay. It got a bit hotter than it does when I use it for navigation using TomTom's app, but not hot enough that I was worried about it. It's a pretty powerful and sturdy phone.
That being said, there's a certain type of person who wants their phone to do everything. I'm not that person. I use the phone for things that it does better than other options. TomTom Go Mobile, for example, is the best car navigation system I've ever used. The dash cam app, on the other hand, was not the best dash cam I've ever used. The video quality wasn't horrible overall, but there was too much glare and reflection, and no way to mount the camera close enough to the windshield to do anything about it.
The other thing I'd be worried about would be battery life. The V20 has a removable battery, so I really don't give a rat's how many I go through. But the V20 is a dying breed. It may well be the last high-end smartphone with a replaceable battery. I wouldn't want to put a non-replaceable battery through that kind of use. It's bad enough that most of them are shot after 18 months. You'd be lucky to get six to eight months out of a battery using the phone as a dash cam every day.
But to answer your question, I would suggest the LG G5 or V20 if you want to try anyway. They have similar specs and replaceable batteries. Be aware, however, that there are very serious problems with unlocked versions of the G5 in terms of its functionality as a phone once you upgrade the OS. That's why you can get them new for ~ $200.00. The LG update hoses them for LTE on some channels. But if you want to use it only as a dash cam platform and don't care about its phone functionality, it probably would work pretty well. I doubt you can find the same power at a lower price. If you do want a good phone as well as a dash cam test bed, then I suggest the V20.
Richard