Welcome to the forum.
I have 0 personal experience with any brand smart / cloud camera, but it is my understanding that they will only upload actual events, not all footage.
If you upload all footage and have a fairly normal drive pattern, you would for sure need a flat rate data plan, but also you would want to be within fairly perfect 4G to be able to offload that much all the time, and something like that you only get in little flat countries with multiple nationwide 4 / 5 G providers like Denmark, where you will often have access to two of them as they have mutual roaming agreements.
Of course if you constantly look at footage via your phone / the 4G route, well that too will eat into your data plan, but once the novelty is over you will stop doing that, and you should also be able to access the camera at least in the car to DL footage to your phone over wifi, that will also have much faster transfer speeds i recon.
Of course if you access what ever your camera have put in the cloud, well then that will of course just eat on your phones data plan, but if you remote access the camera and brose footage on the memory card in it, well boty oyur camera SIM and your phone SIM will be hit on the data side, the camera sim uploading and your phone SIM downloading it.
When you have gotten some footage under the belt, you can try to put the memory card in a card reader on PC, there you can then highlight a whole days worth of recordings to gauge how many GB you actually generate in a day, this amount change a bit depending on the resolution - number of cameras, and the bitrate that is used.
Some cameras will allow you to select a lesser image quality / bitrate, but you should never use anything but the very best option here. If you are starved for room, you should get a bigger Memory card ( today i would not recommend less than 256 GB no matter what camera you have )
I personally prefer to review my footage on my PC, and its nice 32" screen, even if my old tired eyes can still read a phone screen, but i am also a immense phone hater so another reason i will go far to not touch that more than a handful of minutes a day.
On the PC with a good USB 3 card reader on a USB 3 port, i also get the full read speed of the memory card, which mean fast transfers and i can playback footage directly from the memory card, something you can not do on a slow card reader where you will then see stuttering and have a really crappy experience if you try that.
Today wifi transfer speeds are generally OKAY and it should not take longer to DL a file than it took to record it, but that do not come close to the 80 - 100 MB/s i get on the card reader.
