Sutter Buttes are definitely an oddball. Could be late pop from the Cascades, could be offshoot of Clear Lake. No consensus in the few papers (mostly descriptive rather than analytical) I've seen.

Lassen is conventionally the southern end of the Cascades, despite being kinked off to the east from the general trend. Recent work also suggests that it's at or near the north end of the Walker Lane (zone along the E. side of the Sierra, someday to be an extension of the Gulf of California as CA and part of the Cascades break off as an island or archipelago and head for Alaska). Only the cockroaches will be around to see it happen. Lassen's roughly lined up with Cape Mendocino so it should be over the current subducting slab (making it a Cascades volcano) - or maybe not - it's close to the southern edge.

Only one of the recent Lassen swarm (which seems to have slowed down already) was big enough to have a mechanism published. Inconclusive. Could easily be a garden-variety Great Basin/Walker Lane swarm. Just have to wait ... the one in NW Nevada has all the attention at the moment because it's had many more quakes, has gone on longer, and has had bigger quakes ... unless you're right and something hot and steamy pops out. If nothing big happens, it'll never be noticed by the people who study such things - just part of the background.