The first time I did some argyrotype solution I make from silver nitrate, what a mess!! Finally following the ware's note I make a good working solution.
Now, I use silver oxyde bacuase I got some but I find no difference in the image made by one or the other method. So a slight difference in weight, dilution don't change much in the final image contrast and density.
Argyrotype work on far more paper than palladium/platinum do. I do not find any paper on which it do not work for the moment. Crane's paper will do the job .I use simili japon without any pretreatment and also use some arche's papers.
Toning. Just use the toning formula you could find on unblinkingeye ( Sandy king's article on kallitype). It works great. For sure to keep the toner longer it is better to applt the toner with a coatin rod and throw it after use. I tone in tray when I do large print and when I know I will exhaust the toner in one session.
Negatives. This process could be consider as the litte brother of Ziatype ( ware , pizzigheli) any POP platinum method. It is sensitive to humidity but to high humidity and really sticky the emulsion get (more than a ziatype emulsion)
I made some print with digital negative but my old hard disk get out of use with all my curve file in it. I am working on saving the work and may have some curve for you . but you could get good result with a platinum curve. finally if you're doing digital neg you need to do the curve on toned print ( if you want to toned them) as the separatin in the low light are quite different from toned to untoned print.