Choosing PCs or NPCs stat block

I need to make sheet that can let you choose between different forms - one for PCs and second one for NPCs. They look different and use some different mechanics, so easier would be doing as two different stat blocks. I saw there was done something like that for D&D 5E sheet, where you open sheet and it's ask you what kind sheet you want to do. How can I make this two different sheets to able to choose from?

Thats a big open ended question that is really hard to answer without knowing your level of webdesign skill. Check out tabs on the CSS Wizardry wiki page, which covers the technique.