Haven't quite decided yet but I would have the z14-30 mm lens for my Z8 and I will have the DX 12-28 PZ lens for my Z50 Mark II as well as the kit DX 16-50mm. At 12(18)mm and 16(24)mm the DX lenses are at f/3.5 whereas the FX 14-30 is constant f/4 (on the Z8). So in low light I might really need a tripod although IBIS (Z8) or lens VR (Z50II) might be good enough. My primary focus (PI) has always been four and two-legged creatures, but with my new ML systems, and with NZ's famous landscapes, I thought I might take a shot at subjects that ordinarily don't move.
Marv
None of your lenses are that long in FL, but your Z8 body is a bit on the larger side. I do not know how long you are expecting your exposures to be, but if they are longer than 1/2 sec. or so, I would not necessarily rely on IBIS or VR if you are looking to make 20x30 prints. None of your lenses, however, have collars for a plate, so your load will be carried by the Z8. If you are shooting from lower heights and do not need to fully extend your tripod, you may may be able to get by with a smaller set of legs. If you want to work at standing height and are working in a windy environment, then you may want a more substantial set of legs so that you are not worrying about your gear tipping over when a gust comes along.
I also think that you should be evaluating the ballheads and legs separately. Not that combined packages are bad, but you may be able to select a ballhead that best meets your needs that is not sold in a package. But really, it comes down to what you are willing to carry. The old adage was that when it comes to tripods, pick two - price, size/weight, quality. You are not necessarily going to get all three.
I bought my Gitzo about 14 years ago and still find it a pleasure when I need a full-size rig with a long lens and FF body and am travelling by car. But when I travel by plane and have to carry my gear around with me, it stays at home and I try to find what is the smallest thing that I can carry that gets the job done. But I also do not do landscape photography.
I recommend going to a local store if possible to put your hands on some gear, especially ballheads. A ballhead that you like and that works well is its own reward. A bad one is a major pain in the backside, and you will not want to use it again. If you do not have a store nearby, watch some additional videos from folks like Hudson to see how the gear operates. Then buy from a place that has a good return policy. I know that many stores offer extended return dates during the holidays, so you may be able to take advantage of that.
--Ken