Basic question about difference between AES256 and ED25519

[skaainet at skynet.be]

Hi all,

What is the real difference between doing:

    - openssl genrsa -aes256 ...
    - openssl req
    - openssl x509
    - openssl pkcs12

and doing:

    - openssl genpkey -algorithm ED25519 ...
    - openssl req
    - openssl x509
    - openssl pkcs12

for the creation of a self-signed PFX file ?

- Is the second way (ED25519 curve) a valid way of working?
- The purpose is to use the PFX file for encrypting emails with s/mime. 
Will the PFX created with ED25519 work equally well in a email client? Why?

Thanks in advance!