Have you tried speaking with a reseller? They should be available and happy to help you with a 1-1 call.
Generally you choose a model based on your throughput (speed) needs. 5508-x, 5516-X, 5525-X etc. are all models with entry level throughput (< 1 Gbps).
Adding/activating IPS features generally reduces throughput and always requires a separate license (it can of course be part of the initial purchase bundle). IPS license types are IPS only, URL Filtering and Advanced Malware Protection.
Remote access VPN (vs. site-site), known as Anyconnect, beyond 2 users always requires a license.
All the licenses mentioned are term licenses and available terms range from 1-5 years.