It can be very tempting to head for the hills with a puppy, but it is important to not do too much too soon. While they may have the energy it takes time to build up the stamina and muscle for a day in the hills and, crucially, a dogs joints aren't fully developed until around 18 months old. Doing too much too soon can lead to joint issues further down the line so best to take things slowly and let them finish growing before tackling longer distances and more complicated walking like boulder hopping and scrambling.
From a year old you can build up to walks of a few hours, but for 6-7 hour trips I'd wait until over 18 months. In the meantime focus on building up your dogs training and introduce them to different environments and the things they will see as well as getting them used to you checking their paws. The paw pads need to toughen up for walking on harder ground so this can be something to work on.
With jackets I have one in my pack just in case, but whether a dog needs a jacket or not does depend very much on the individual and their natural coat so do go by your dog, if they get very cold and wet in heavy rain then maybe a light raincoat would be an option. My lot are all double coated though and the rain doesn't soak through to the undercoat. They do have dogrobes to put on in the car/when at home though to dry them off a bit.
If you haven't already, train recall to a whistle as well as voice. The sound of a whistle travels much further than your voice and also doesn't give away any emotion.
I walk mine on a hands-free belt with a canicross line (when they can't be off-lead), this gives us all more freedom. A harness with a handle is handy for walking them on, this means there is no pressure on the neck if there is a sudden jolt and the handle means they can be lifted/assisted over stiles, fences etc if needed.
In my first aid kit I have PAWZ dog boots, these are handy to protect a paw injury if one was to occur preventing dirt getting in. I also have piriton in case they get a bee or wasp sting to the face, ask your vet for the right dosage.
I don't like waiting for a dog to be ready for the hills so my youngest was 14 months old so the time until longer walks were possible was the building up stamina time anyway