No e-ink tablet is very good at displaying PDF. Some are not
as bad, and you can use tools like
k2pdfopt to try to overcome the inherent flaws in PDF, but if you are going to be reading mostly PDF, you really should get a tablet.
And like Yapyap said, there really aren't any frontlit ereaders without touchscreen. You might want to try out different touchscreen-enabled ereaders to see how sensitive they are (and how noticeable fingerprints really are) but if you decide that you really don't want one, well, you will have to go with old tech that doesn't have frontlight. You can, however, find lighted covers for (probably) all of them.
All ereaders are bookshop-agnostic, as you can sideload anything you want (and use
calibre to format-shift), with the exception of the most recent Nook Glowlight, which restricts the memory to store-synced books except for a tiny fraction of the built-in memory -- and doesn't have an SD card.