those that have okayed saying tehillim “nowadays” after sunset are not sod and sometimes anti-sod gedolim. the mekubulim still oppose it.
while I do not live by the rules of sod, i do not say tehillim after sunset except on shabbos. in my mind, using tehillim to pray is something very “sod-like” and the remuzim, rushei teivos, sofei teivos, etc work only in the world of sod. since i am in the world of sod, i play by the rules of sod. when in rome.
(i understand an argument can be made that tehillim functions in guluy also but that seems like a stretch. i believe that the power of tehillim is different.