OK then, you do need to be aware that some users of the A129 Duo have had issues with it shutting down while parked, and of it stopping while driving and beeping. This does not affect everyone using parking modes in this cam and whether you will experience these issues is anyone's guess. Please read the threads on this site regards this before choosing this cam. Also look there to determine which SD card you'll want to buy. Dashcams are particular about SD cards and reliability so use only one you find well-recommended here for the A129 Duo to avoid problems
Powering the cams will require USB- type powerbanks which will need charging between uses, or you can use the Cellink Neo powerbank kit which automatically charges as you drive. It does require 45 minutes of driving to fully charge so if your daily drives are shorter than that it might not be the best idea. You can guestimate powerbank capacity by knowing that 2 cams will use about 1000mA per hour for regular recording and nearly that much for low-bitrate recording while parked. Based on where everything is mounted you might need longer USB cables to power the system. Again these need to be high quality with large all copper conductors and not the cheaper CCA type cables. 24ga is a good wire size, and Monoprice is a good place to source these.
If you don't think the A129 Duo is for you we can find alternatives, but they will either be higher priced, without the low-bitrate parking option, or with lesser-grade sensors.
Phil