A:
check with your provider on how many channels they operate their internet on and go from there. for example cox operates on 4-6 channels depending on area. so it is pointless to buy a modem that handles over 12 channels. for an ISP to make a channel upgrade takes a lot of time so i would not worry about that at all. if you want to go cheap beware it may have dead spots i would recommend the following.
NETGEAR - AC1750 Dual-Band Router with DOCSIS 3.0 Cable Modem
NETGEAR - AC1600 Wireless Router with DOCSIS 3.0 Cable Modem
these are combo units modem wifi. saves on clutter