Any BT package that has "totally unlimited" usage will not be throttled regardless of traffic or time of day. The Home Hub can be swapped out for any ADSL router but I don't know about the 'modulation mode' as I'm on VDSL.
BT aren't necessarily the cheapest, but they do throw in some nice extras. Free WiFi Hotspots, Antivirus and newly annouced BT Sport are all things to consider. The only thing that I can fault them on is customer service via telephone which isn't great though you can mostly get by using the BT Care forums.
Unlimited BT Infinity 2 Down 73.6 Up 9.7