Use wpad-mesh-wolfssl since the wolfssl library is already in the ROM.
Wolfssl has been frequently updated so you'll need to start with a new ROM having the updated wolfssl and the packages that it uses. Otherwise installing wpad will try to load the new wolfssl while the other one is still there, and it will run out of space.
The cram-down can be done with attendedsysupgrade or the image server.
wolfssl is currently being abandoned for mbedtls.
While that is 'a' plan (not 'the' plan, yet), it hasn't happened, yet (not in master, only wpad-mbedtls packages have landed there so far) - so wolfssl is still the way to go (unless you really know what you're doing and/or building from source).
Ach. It seems I was trying to add package but i've exceeded free space. What are my options now? what can i safely remove?
You can't, you have to create an image with the excessive packages removed.