Your honest opinion on backpack hiking carriers and structured toddler carriers

So my son is 16 months old and has low muscle tonus, he is probably going to start walking at about 2 years old. I use different woven wraps and a ring sling to get out and about when the stroller won't work, but his dad doesn't know how to use them (not even the ring sling). I was kind of looking forward to using a backpack carrier for hikes this summer, since I get sweaty really fast. I also like the extra storage and the little sun shield. I think it could be useful when we take solo hikes, so I don't have to carry my kid and the backpack. And of course it'd be great to take turns with the dad when we go hiking all together. I asked my son's physical therapist what she thinks about those carriers. My son sits up independently and when he's awake she's okay with him being in a backpack carrier. But she doesn't like him (and any other kid) falling asleep in them because they will slump down. She suggests buying a structured carrier. I'm not really happy about that, because I'm a woven girlie and I actually already own enough of those. Also, the only upside to a structured carrier is the being able to take turns with dad. Does anyone have any experience with sleepy kids in backpack carriers? Of course I won't doubt her professional opinion, but maybe there are different brands that offer more support or there are some hacks like a neck pillow. Also, does anyone have experience with hiking in a toddler carrier? Where we live it gets hot and trails are usually steep.