Ah, I misinterpreted your statement about VSX. Apologies.
Your best bet here is access roles. You can use access roles to match against AD security groups and/or entire OUs. If a user is in both AD groups, and you need differential policies for those groups, then you need to create multiple access roles and use those in your rules. When you do this, you no longer need to use "legacy user access" rules with the RemoteAccess community. Just use the access role in the Source column and make rules as usual. If you want to restrict/allow per AD group (access role), then build your policy that way, whatever you were expecting. You can also configure the access role to apply when connecting from a specific VPN client, so the user group + VPN client can be bound together. IIRC, all the mobile device VPN clients are the same (Capsule Connect) so I don't think you can limit "users with iOS client" and "users with Android client". You can choose between the Endpoint Connect client (Windows/Mac) and mobile clients (Capsule). Sounds like you're about to have a bunch of Access Roles. 😄
Keep in mind 2 distinct components: authentication vs. authorization. For decades, we've thought we had to consider these as one (well, RADIUS does). However, that's not true. 🙂 Don't fret about the authentication portion too much. If you want limit VPN-eligible users, that's ok and you can do that with LDAP groups in SmartConsole if you want. The access policy takes care of the authorization part. Keep that in mind and build the policies accordingly and you'll be in good shape.
You still need an LDAP account unit to pull user identity and information, and the gateway will gather all of the LDAP server group info into the unified user record, and update the identities. Be sure you have Identity Awareness enabled, do not use AD Query (it's effectively broken anyway and not worth the trouble), and be sure the Remote Access source is enabled. Preferably, use Identity Collector as well (replacing AD Query).
When users connect, you can run "pep show user all" to see the user details of the user records.