is that separatist movement in Silesia aggressive? Are trips safe?
Lower Silesia is to Silesia as West Virginia is to Virginia or Lower Saxony is to Saxony.
In other words, Lower Silesia is not in Silesia, and has very little in common with it nowadays.
When modern Poles say "Śląsk" (without a qualifier), they usually mean either the area formerly known as Oberschlesien (Upper Silesia), or województwo śląskie, depending on context.
Dolny Śląsk is usually not included except in some contexts having to do with prewar history. People from Dolny Śląsk generally do not consider themselves Silesians (unqualified). They may consider themselves Lower Silesians, but not Silesians.
Even the origin of the local population is different. The (almost entirely German) population of Lower Silesia was expelled after WWII and replaced by Polish refugees from the eastern areas of Poland that it lost after the war. There were few Slavic inhabitants before the war.
In (Upper) Silesia, not all of the Germans were expelled, and there was a significant amount of Slavic inhabitants before the war.
Województwo dolnośląskie almost, but not quite, coincides with the pre-war Niederschlesien. Ziemia Kłodzka was historically never part of Silesia, but of Bohemia.
A good part of Niederschlesien now lies in Województwo Opolskie, as does a good part of Oberschlesien (About half and half).
Województwo Śląskie, on the other hand, contains large areas that were never part of Silesia, like Sosnowiec and Częstochowa.