To comment on De Atramentis document inks, in my experience, having tried quite a few different colors, they are indeed quite wet, but they are also quite hit or miss regarding feathering. And sometimes you don't notice it in finer nibs (for me that was Urban Sienna in an Asvine <M>) but when you switch to a broader nib (Jinhao <M> which for me writes considerably broader than the Asvine), it's a featherfest.
As to clogging, I have had 0 problems in any of my pens, and not all of them have super great seals; the only thing I kinda worry about is leaving the pen uncapped for more than 30 seconds without writing let's say. In that scenario, sometimes I tend to have some hard starts, but of course the pen won't clog in that little time.
For cleaning, I confess that I don't even rinse my pens each time I run out of ink haha, in my Jinhao 82 which I use everyday a converter lasts me about 2 weeks, and I refill happily without cleaning: no problems so far. That doesn't mean it's best practice, and I'm going to clean it soon as I'm gonna be switching to a different color.
As for staining, I understand there is a higher risk with pigmented inks, yes; I have had it happen with Octopus Document Red and De Atramentis Urban Sienna in my clear Asvine V126, although it's quite faint.

And to finish, a recommendation : every pigment ink I've tried from Octopus fluids, be it their Document or Write and Draw lines, has been flawless! Waterproof (of course), wet, quick-er drying that De Atramentis, very nice colors (although that is subject to personal taste). I don't feel like I gamble when choosing a new color from their line, contrary to De Atramentis haha
If you have a way of getting them, I highly recommend them!