From what I have read, and I haven't looked in detail, the IQRouter is an old TP-Link piece with semi-proprietary firmware running on it. From an Amazon US review
The IQRV2 is a rebranded TP-Link Archer c7 with a (mostly) open source firmware. The Archer c7 is, at this point in time, rather dated and is a third of the cost of this router.
If so (and there are other similar statements on the Internet), you're not going to get more than ~150-200 Mbps through it with SQM enabled.
I think there are better choices out there than the older C2600, including "mvebu", "ipq40xx", and later-generation "ipq806x" devices, many of which are available at US$100 or less. It all depends on what you want to do with the device in terms of routing, SQM, VPN, and various wireless configurations.