"Today' tag and planning you day based on contexts
On your first question about using a 'today' list - what software are you using? or are you using paper? I for instance use Evernote and I have a separate tag that I add onto any next action that needs to be done today. That way, I don't lose the context for the next action but I can still easily pull up just the list of actions I need to get done today. Once those are done, I can then move onto the full next action lists.
And on your second part, I absolutely use my action lists to plan my day. I'm looking right now at my lists and I see that my @email has over 60 items on it. This means that I need to create about 3 hours in the next day or two to get to everything on this list. No way that's happening if I don't block time off my calendar to sit and get through it all. And similarly with @home, @office, @errands, @internet, and so forth .... I plan my day based on what's happening in my context lists.