I know nothing about QEMU, but ...
If you use a regular x86 install, and dd the whole image, it'll will wipe the partition table you
had created. The partition have to be resized, and FS reextended afterwards.
gparted is a good tool for doing it, assuming it's compatible with qemu.
another option is to create the partitions, and manually write the root FS to sda2, and the kernel to sda1
It'd be as adding a 2nd install, as I've described in Sysupgrade help for x86_64 - #14 by frollic
and no, you don't need to resize /boot, since it only contains the kernel, it's the / you're after (I'd assume).