1I'm considering using a panning clamp or an Arca-Swiss P0 or other ballhead that puts the rotation on top of the ball so that the ball is doing the leveling.
2The other option is a leveling base for a standard ball head.
3I suppose a third option is combing both, but I'd like to avoid added cost and weight if possible.
4The main thing I'm unsure of is which system allows you to be able to tilt the camera up or down and not always have the horizon centered?
5Also are multirows possible without these setups or is the standard pano head setup with both axis rails needed for that?
6I've seen many posts on the web stating that you can't tilt up or down with the rotation above the head.
7Then I did some more digging and found people saying that about the standard ball head with leveling base setups. Both sides appear knowledgeable, but clearly one is wrong.
8Another thought I had was that maybe it's not possible to tilt up or down with the panning clamp, but it is if you ad a nodal rail to that setup?
Two things to clear up before I actually reply. This is the internet; it is filled with conflicting opinions. Some of those opinions will come from people who have no, clue as to what they blather on about, soem will have some clue, and others might actually have useful answers that relate to what you want to do.
And that brings up the second thing which is actually two questions:
A) What is the subject matter that you want to make panoramic photographs of? Roughly speaking there are landscapes where precise geometric rendering is not critical; and cityscapes and architectural studies where good geometric rendering is critical to the finished photograph's success. The hardware needs are no so critical for the first case - especially if the differences between near and far elements in the photo are slight to non-existant. The larger those near to far differences are (based on your lens focal length choice and basic subject to camera distance) the greater need you have for specialized hardware like a "nodal slide".
B) What is the intend use of the photographs?
Only you can answer those questions.
On to my answers , which are based on my experience, to your specific concerns.1
Unless you are just looking to do quick panoramas my experience is that having rotators at the top (camera platform) and base of your tripod head makes life a whole easier. Not just for panoramic photography but anytime you use a tripod. I have four heads that I use regularly : from larger to small laods they are a Foba ASMIA (http://www.bhphotovideo.com/c/product/247458-REG/Foba_31_0118_ASMIA_Double_Pan_Tilt.html);
Arca-Swiss B1 Monoball (modern equivalent = Arca-Swiss Z1sp); Arca-Swiss D4M; and Arca-Swiss p0 2 & 3
For really precise architectural and product work I will use a leveling platform - A Manfrotto 338 QTVR Leveling Base (http://www.bhphotovideo.com/bnh/controller/home?O=&sku=554092&Q=&is=REG&A=details
) but I put it between the top of my tripod head and the top level rotator(A Really Right Stuff PCL-1) on the ASMIA head, not underneath the head. As a tripod head is already an excellent leveling platform for my
work I don't see a need to put a leveling base underneath it. But in most cases I do not use one.4 & 5
For that purpose I use a larger panoramic mounting rig, essentially it is the PG-02 Omni-Pivot Package ( http://reallyrightstuff.com/ProductDesc.aspx?code=PG-02-Pro-OPP&type=3&eq=&desc=PG-02-Pro-Omni-Pivot-Package&key=it
) but withthe longer CB-18 bar instead of the shorter CB-10 bar. This has to do with the size of the camera bodies I use. I can shoot with the center row level or tilted up or down. However most of my work is either landscape or interiors, including geometrically complex industrial interiors. If you are doing landscapes, you may not need or want that degree of precise control and can do great work with a head with a panning camera platform and possibly a nodal slide. 6 & 7
The definitive answer here is simple: Whoever said those things is ignorant. 8
Using a panning clamp has nothing at all do with the angle you set your head to. rotators are just another joint and work independently. The purpose of a nodal slide is to center the entrance pupil for the lens in the axis or axes (if shooting multi-row panoramas) of rotation you'll be swing your camera around.
The reasons I like the Really Right Stuff (or similar) approach to panoramic support gear is that it is modular and I can use all of the components or just the ones that I need for a specific shot. I can also use them for other kinds of photography: still life, macro work or securely supporting the camera in positions a simple tripod and head cannot fit into. It's all about having options. Whether I choose to use them is a different matter.
I specifically like the Arca-Swiss, Foba and Really Right Stuff gear I use because it's all very well made and very, very reliable. I do my best to spend my money very carefully on these types of things.
The stitching software I rely on is PTGui Pro although the version of PhotoMerge in Adobe Photoshop CS6 is much better than it has been in earlier versions.
I hope this helps. And Bart is right: Once you start many of your questions will begin to present you with the direction you need to go in for the answers that will work for you.