Sorry for the late reply.
Yep, but remember you'll have to remain in that channel for the lifetime of the objects. ArenMook pointed out an issue I overlooked though: TNet 3 more closely manages object lifetime, so to avoid the issues he mentioned you shouldn't use any of the Target.___Saved RFCs. There might be some other issues involved, so consider ArenMook's advice (don't use static objects). Though, I don't think it'll cause any issues if you're just using them for persistent singletons (even with saved RFCs). But ArenMook's strategy of instantiating your managers from the OnJoinChannel notification is just as effective as static TNObjects and you'd be able to use saved RFCs without worry. And, of course, if the dev himself discourages something, then you probably shouldn't start a new project with that thing. Could be phased out in later patches.
You're right, a call to JoinChannel without being connected to a gameserver results in a non-async load level. If connected, the server sends a ResponseLoadLevel (and a bunch of other stuff) which does lead to LoadLevelCoroutine being started.