I am using 2022.10. version (
https://github.com/koreader/koreader...s/tag/v2022.10)
and PDF performance is very, very good.
My PDF-s are scanned books (around 300-500 pages) and around 30-50 MB.
Keep in mind that eink display have intrinsic permormance limits, in terms
of display refresh time which is around 0.4 S and does not include any
additional cpu time for processing of data before displaying it.
So, I can recommend Inkpad 3 for Koreader 2022.10. "Muhara" version .