Quoting golinux@??? (golinux@???):

> Can't say for sure. Wouldn't Comcast/Spectrum/RoadRunner(TWC) be
> able to throttle traffic more effectively using their in-house DNS
> service? Maybe unbound escapes their reach?

I don't think this is likely for various reasons including the fact that
traffic throttling that can be evaded just by using a non-default DNS
nameserver is excessively feeble traffic throttling.

On available evidence, although there might have been multiple sources
of badness for all I know, you had at least _one_ identifiable problem
source in the form of really bad ISP DNS nameservers. (As I think I've
already said, this is about the opposite of surprising, to yr. humble
servant. ;-> ) We can have fairly high confidence in the foregoing
for the simple reason of that badness having gone away when you swapped
in Unbound.

If I were charged with doing traffic throttling at, say, an ISP, I would
do it with iptables/netfilter or equivalent, i.e., at a lower level in
the network stack than where DNS operates.

(I won't torture you with the '7 layer burrito' speech infamous among
all junior sysadmins and aspiring network engineers, who are obliged to
commit to memory the OSI Reference Model before interviewing for jobs.
https://www.6connect.com/blog/moment-internet-history-osi-7-layer-burrito/ )