Building on the earlier suggestion, be careful with wireless triggers in the cold. I would suggest comparing these:

• Nikon MC-DC2 Remote Cord: Reliable cable, 0ms latency, draws zero independent power.
• Vello ShutterBoss II Timer Remote: Advanced intervalometer, but AAA batteries drop voltage fast in sub-zero temps... Wired is definitely safer for Iceland landscape work so your shutter wont lag. Make sure to keep your gear dry!

unfortunately, many of the online gear lists are filled with fluff that wont actually help you in a place like Iceland. I have had issues with generic batteries failing suddenly in the cold, which is quite frustrating when you are trying to capture a long exposure. Skip the expensive grip and just get a few extra Nikon EN-EL15c Rechargeable Li-ion Battery packs. Keeping them in an inner pocket close to your body heat is much safer than relying on a heavy grip that might not even provide the endurance you expect. For landscapes, a standard plate was not as good as expected for vertical shots, so i recommend a simple SmallRig L-Bracket for Nikon Z6 II/Z7 II 2947 instead of a full cage. It provides the stability you need on a tripod without the unnecessary weight. Reliability matters more than gadgets when you are out in the field.

I would suggest skipping the cage. Just be careful and grab:

• SmallRig L-Bracket for Nikon Z6 II 2258 for landscapes.
• SanDisk Extreme PRO 128GB CFexpress Type B cuz cold weather lags cards.