SSH 2 only supports the 3des-cbc cipher because that is the only cipher that is REQUIRED by the SSH 2 specification (http://www.ietf.org/internet-drafts/draft-ietf-secsh-transport-24.txt). Many servers however do implement the aes128-cbc which is RECOMMENDED. MidpSSH may look to implement this as well in future versions.
For key exchange in SSH 2 MidpSSH supports the following public key algorithms:
ssh-dss
It does not current support ssh-rsa. The DSS algorithm is the only one required by the specification (http://www.ietf.org/internet-drafts/draft-ietf-secsh-transport-24.txt), however the RSA algorithm is RECOMMENDED and supported by many (if not all servers). In fact there appear to be some servers (OpenSSL 4?) that only support ssh-rsa. Given the specification I believe this is a bug. You can likely enable ssh-dss in those servers; take a look in its configuration file.