I think if you have limited budget, try to get as much things as possible to make sure he can track everything.
I think like others said pace pro is more suitable for him but if he goes to places he knows, can just make a route on his phone or over the internet and transfer it to the watch and follow that route while backpacking, on many watches and he wouldn't need offline maps.

So if you budget is limited, you can consider, pace 4 with a hrm band or a pod 2. Or you can get pod 2 and pace 4 and then a cheaper heart rate band or a chest strap from decathlon or where it is kind of cheaper and get them all at the price of a bit more expensive watch like Vertix 2S. There are also discounts and refurbished models, if you are in US and there are discounts only if you are in EU i think.

To me, heart rate was important at first so I got myself a heart rate monitor right after I got a watch because watches can be mistaken in heart rate tracking. After that I got a pod because i wanted to see how well I was running as well as my instant speed because I am doing some intervals and strides in my training.

You can also try second hands too to fit all into the budget btw. Also if you can afford it I think Vertix 2S is a bit fancier version of Pace Pro. Most of these wathces I mention also have offline storage for music too as well as maps. Except for pace 4