Yes, Regions is the common way to limit per-call video bandwidth within and between sites. Regions will affect all devices with that region assignment (via the Device Pool).
If you have a specific Jabber client or set of Jabber clients where you want to limit video bandwidth between the Jabber clients specifically, you can edit the jabber-config.xml file (directly or through the Service Profile if you have CUCM 12.5 or later) with the parameter J2JMaxBandwidthKbps which specifies the max bandwidth to be used for Jabber to Jabber calls, including video.
But I'd go with Regions.
Maren