I have a scratch vanilla cupcake recipe that I use, and I would like to just quickly doctor it to make white chocolate raspberry. I'll just be using fresh squeezed raspberry juice, and white chocolate chips. But I'm wondering: to get the white chocolate flavour to really stand out, will it be better to melt the chocolate and fold it in or just add in the chips normally?

Have you "doctored" this recipe before? If not, most scratch recipes can't just be changed to whatever without adverse effects. By subbing raspberry juice for something (milk maybe?) you are changing the PH of the batter, the fat, and the sugar. That's a lot to change. You probably would also need to change other areas of the recipe, too.

You can try just making that substitution, but it may not work, and/or it might work in a small size but then not in a bigger size (ie it might sink or not rise right).

If you have already played with the recipe before, then nevermind. Just thought I'd give fair warning in case you hadn't tried it. I've tried to learn a lot about baking science and have started playing a bit with tweaking recipes and it's definitely like a science experiment - fails more often than it works!