I've, amazingly, run out of space on my PW4. I've been there for a while -- I think some PDFs from archive.org account for the biggest jump -- and focused on finishing what I've left unread, but it's time to get some more space as I'm loath to throw out books

I'm also tempted by the new options with warm backlight these days.
I can't buy the latest PW, though. I don't want to let my ereader sync my private notes to Amazon because I can't sideload their book and have to connect to wifi instead. The other problem is PW is now sold through resellers in my country and it is priceyyy! I think I paid $140 for PW4 without ads and now I'm looking at over €200/$220 with. I can't blame world politics on this, the prices were just as high when I first checked last autumn.
My Mom has a Kobo Clara BW. It seems well priced and I love the screen and the backlight

Even without backlight, it looks a good bit nicer. Lowest backlight with night mode is also much better on Clara BW. The big bezels are something I'd like to keep from PW4 (as opposed to PW6), although I'd prefer PW4's flat screen. The back is much nicer, PW4's rubbery back feels cheap to the touch and comes off easily.
My problems with Clara BW are no functioning landscape view (absolute must for reading PDFs) and it couldn't open a 50MB PDF (the pages rendered white until I zoomed in, but reading a whole book like that is unworkable). PW seems better at this, although it mostly fails completely at >100MB sizes. I'm a little surprised since they both seem to have a single 1GHz CPU. Any idea if this all works better with KOReader?
Clara Colour has a better CPU and having color is nice, but I've read the black-white contrast is not as good as Clara BW. How does it compare to PW4? (Carta 1200?)
I also had a look at Tolino Shine 5 -- it seems to a sort of cheaper Kobo rebrand but people say it's slower (worse CPU?) which would probably pose a problem with the PDFs. Also no landscape.
I don't have a clue what other manufacturers have on offer at all (nor Kobos beyond Clara). There must be something I'd like not far from BW's price. Surely under $220.