I use a Garmin chest strap HRM for Zwift - it connects via ANT+ so I also have an ANT+ dongle for my Mac. (I also connect my Wahoo trainer via ANT+ as I've found it to work better than Bluetooth).
I use this same HRM for outdoor riding - connected to my Wahoo head unit.
My Garmin strap is starting to show a lot of wear (I've had this one for a few years and it's been through the washing machine many times). I'll probably look to Wahoo for a replacement - I'm intrigued by these wrist/arm straps. My Fitbit isn't very accurate but I think it's because I keep it too loose on my wrist. Something with a fabric strap probably works better than a watch in this regard.