Best Way To Switch Levels?

Hi

So I am trying to make a sequence for my game where it opens to the main menu level and when you click new game it will play the intro text which is in another level. Currently I just use open level(by name) which works fine but when I switch from the intro text level to the playable level the playable one starts untextured for a little as it loads. What would be the best way of switching levels that would work when i add more. I am trying to understand level streaming and the use of a loading screen but dont understand how to do this. Also if I use level streaming how would I switch gamemodes since my main menu uses its own gamemode.