Hey @Wally. In order for the cameras to remain online and active, they must have that stable connection to the internet, which requires the minimum and recommended numbers that you have stated. Therefore, even when in the Modes settings to disable the cameras, the cameras will need at least the minimum to remain online. Without the minimum, they may fall offline or not capturing any events, as well as be unable to go into the Live View. In addition, even if they only get the bare minimum upload/download needed, you may see video/audio quality concerns from a poor connection.
I recommend giving them a try to see if it works out, but considering that other devices in the home will be connected to the internet as well, I would also recommend looking into seeing if you could upgrade your speeds even ever so slightly to accommodate.