Summary: It's all changes in capitalisation and writing things together or as two words.

Demonyms referring to people from cities or districts should now be spelt with a capital letter, as those referring to nationalities already are – e.g. “Krakowianin” (Cracovian)

Either lower case or upper case may be used for what the RJP calls “unofficial ethnic names” (some of which are used pejoratively), such as “Angol”/“angol” to refer to an Englishman (who should properly be called “Anglik”) or “Żabojad”/“żabojad” (literally “frog-eater”) for a Frenchman (who should properly be called “Francuz”)

Brand names should be spelt with a capital letter also when referring to an individual specimen, e.g. “Zaparkował czerwony Ford” (“He parked a red Ford”)

The prefix “pół-” (semi-) should be combined with the rest of the word in compounds like “półżartem” (half-joking)

The prefix “nie-” (un-, non-, not) should always be combined with adjectives and adverbs, regardless of semantic interpretation – previously writers could opt to write the words separately based on the specific meaning

Greater use of capital letters:

in proper nouns denoting geographical names like parks, churches, estates, castles, bridges, squares, avenues, etc. – the exception being the word “ulica” (street), which remains lower case. For example: ulica Józefa Piłsudskiego, Aleja Róż, Brama Warszawska, Plac Zbawiciela, Park Kościuszki

In the names of prizes, e.g. “Nagroda Nobla” (Nobel Prize)