This article here says that one can shift/upgrade from win 10 x32 to win10 x64 through a clean install, provided, system is upgraded from win7/8 x32 and activated. groovypost dot com/howto/switch-between-32-64-bit-windows-10/ At the end, author conveniently forgets to talk abt activation status on fresh installed x64 system. Queries: Is it possible to upgrade through this route? Will activation stay on migrating from x32 to x64?
Yes, it is. You need to skip the product key entering part & your Windows will be automatically activated after connecting to internet.