ive done a fair bit of this sort of thing and a couple of things i have found are
hot pressed watercolour paper looks ace if you print it with multiple passes ,good registration is needed
you will need a lot of ink so refilling kit is a lot cheaper
not paper is ok for some things but will always look a bit "fuzzy"
sized and not sized gives a different result
cannon printers are more robust for this sort of thing than others
building the image from different layers works very well ,start with an underpainting layer at say 20% then image layer one at 30%,let it dry and repeat it then add the dark stuff and details at 100%
it sounds complex but with photoshop and a bit of practice with layers and filters you will get the hang of it
sometimes it is worth scanning a print of several layers and then using that as a layer rather than combining the layers in ps
re paper a4 wc pads tend to jam so i get it cut with a guillotine to slightly under a4 and adjust image sizes in ps
do test prints on 150 gm basic wc papers to get the layering correct before you spend a lot on handmade 300 gm
i havnt worked out how to get rensho and the like not to jam
the card that is sold for making cards is horrid and looks cheap however well you print on it imho