Ellie Young has published a revised version of her thesis as a book. Can't remember what it's called.
In contradistinction to greg z, I would not be so categoric about ruling in or out papers and/or sizes.
As you note yourself in your OP, alt printing is often a journey of discovery. If you try a paper and find it produces the results you like, then it won't matter a jot whether it is jammed with resin internal sizes and made of mashed up old matchsticks rather than pure unblemished rag.
Keeping things simple and sticking with one paper and only varying process (dilutions, sizes, coating method, whatever) one variable at a time is a reliable way of achieving consistent results; but of course only if consistency is your aim.
I've been making salt prints, Namias sepia prints & cyanotypes for two or three years now.
One thing I still have to force myself to remember is that when I mix two equal volumes of the same dilution ratio of two materials, I am doubling the dilution of each in the total final volume
The only other couple of things I'd say are:
If you're not using a paper that you know is absolutely alkali-free, acidify it before trying a salt print on it (I use Citric acid, others use different acids. There's an interesting thread on acidification of paper with Sulfamic acid to read in the alt process subforum). It'll reduce the chances of chemical fogging.
And do use Citric acid in your sensitiser. Same reason - reduces risk of fogging (thanks NedL

)
Oh, and those papers that are recommended by the (usually American) writers on alt printing?
Most of them either unavailable or spectacularly expensive in the UK (though being in London will help you in that regard as you have local access to merchants like Shepherds, Burt and John Purcell).
Cheapest source I've found for nice watercolour papers (eg Fabriano) is via the Great Art (Gerstaecker) website. If you sign up to their newsletter and open an account, they send you offers all the time, some of which are amazing bargains (most months they seem to have a 20% or 30% off everything offer). They ship from Germany but it rarely takes more than 3 days. Of course once Brexit takes place this'll stop being any good to us, but in the meantime, fill yer boots, as they say
anyway, good luck, enjoy yourself.