Where I get confused logistically is do I keep several next action lists going at the same time and if so how do I move to the day to day in that when I've got several projects on the go or am I just overthinking this which is totally possible too.
As others have responded above, yes you keep several next action lists going plus your calendar. You also have a Projects List and a Someday/Maybe List.

The way you interact day to day will depend very much on the nature of your work and life. For some, their work is very prescriptive and they will not have much discretionary time. For many, all we have is discretionary time with the odd meeting parked on the calendar. Basically, you want to review your lists as often as you need to to be comfortable that you are doing the most appropriate action at all times.

An example. Every morning I get into my office, clear out my tickler file and check my calendar. I now have a picture of my day (e.g., today, I have an hour and then I'm off to a meeting all morning but the afternoon is free in the office). Then I review my two @work next action lists which have items from most of my 43 work projects plus a lot of non-project actions. This is to remind me of what is already on my plate and sometimes something jumps off that needs immediate action.

Only then do I switch to my email. I can then process my email inbox to zero if I have time. But more importantly, I now have some perspective with which to judge these new emails. Is this request that came in last night more important than those other items on my list? Maybe - maybe not.

Hope that helps. Keep at it and check out all the valuable information on this website and in the forums. Ask as many specific questions as you need to - folks here are great at answering!