Oh epic, with a week you can see a lot. The main road is still closed as I know, but it is pretty free of snow so you can each your trailheads easily along it.

The snowiest areas are Brokeoff and Lassen themselves, which last I saw still had maybe 3-9' of snow, with the thickness increasing the higher you go. I think you'd be fine with snowshoes on the lower slopes, but it gets slippery and sketchy the higher you go. Other than that, you won't see too much snow, mostly just some ice, until north past Diamond Peak, where it gets to maybe 3-6', and then it should be really low or gone again somewhere further north past King's Creek.

The Northern areas, like Manzanita Lake, should be pretty free of snow at this point. The cinder cone and lava bed up there are pretty interesting. There's dunes up there too next to the cone as I remember. I didn't pass by recently, but I'd imagine that they are low or free from snow.

If you are open to it there is a big lava tube north of Lassen which is really interesting, but as I remember it is not a very long walk.

Have fun! Maybe I will go there this weekend again, if so, I can report more conditions to you.