If you’re talking about the language, Czech was heavily Russified after
the war and that removed a good percentage of Germanic words and
replaced them with Proto-Slavic words, Polish has more Germanic words
than Czech at the moment.
I’ve already noticed there are many similarities between Czech and Russian. They share many words that Slovak doesn’t use. I’m doing a Polish course on Duolingo and I’ve noticed it has sooo many borrowings. Many of them sound like they were borrowed from English, though.