About browser history
I installed the browser few hours ago and imported my favorite data from chrome. The browser seems to connect with google chrome, but I'm not sure whether the data of chrome is not affecting if I clear the history data here. It might be OK, but I want to make sure before I clear all the data.
Don't actually understand what you're asking here.
If you are asking whether the Vivaldi feature "Import Bookmarks and Settings" will change anything on the Browser imported from; then the answer is "No it won't".
Once the Import has finished, nothing else is read from the other browser - Import is NOT a synchronisation feature.
However, it might be safer to keep the chome data for a while until you are sure that everything you need HAS been imported.