I have 4 of them but haven't got them planted yet. I plan on putting 3 of them in full sun and the other one where it gets sun on and off during the day.
Sorry I can't be of any real help.

I'm about to move mine to a sunnier spot. It currently gets sun only from 11:30 a.m. to 1:30 p.m. and is struggling a bit (little flowering). I will place it where it gets full a.m. sun, but shade in the afternoon

Depends a bit on which thalictrum it is...I have two rues, one gets full sun and would probably like even more (!) and the other gets almost full and seems happy enough. I think they have very attractive foliage--in shape and color.

Thalictrum aquilegifolium, known fondly in this household as "Koosh ball plant," gets afternoon shade yet gets burned out and cripsy looking by mid-summer. Really, mine might have a recurring mildew, but it does look like too much hot sun. Mine don't even have very good flower color--don't know why I haven't done away with this plant.