I have 2 ipsec tunnel active on ASA5505 (secplus license).
I would like to activate sslvpn also. Is it possible or there are issues in keeping active both services?
Yes you can run both IPSec and SSL VPN tunnels at the same time.
For SSL VPN, it comes with default 2 license, meaning you can have 2 concurrent SSL VPN tunnels.
If you need more, then you would need to purchase the AnyConnect license.