How much knife for hiking
Hardly any knife all. Hiking is (or should be) about minimalism. You should be carrying as little weight as possible. Too much gear gets in the way.
A 3-4 layer 91mm swiss army knife is about the most I would take on a single day hike. Some hikers refuse to carry anything more than a 58mm Classic SD, even on extended multi day hikes.
With all this bushcraft stuff on YouTube promoting larger fixed blades, how many people head out into the woods with a folding knife? I’m expecting a Buck 112 slim to try out soon on some small hikes. Can’t image needing a 6” fixed blade unless bushcraft is really your thing.
Plenty of people use swiss army knives for bushcrafting, if that's what you're interested in.
The Camper and the Huntsman are both popular choices.
The Camper is 3 layers. It has 2 knife blades, a saw, an awl, a corkscrew which is useful to untie knots, a flat head bottle cap lifter, and a can opener which can work as a #2 phillips driver.
The Huntsman is 4 layers. It is the same as a Camper, but with an extra layer which has scissors and a hook.
The Camper and Huntsman usually come with smooth soft plastic celidor scales, but sometimes they also come with more rugged textured hard nylon scales. The nylon scales are generally considered to be superior, but they aren't very common.
The Farmer and Farmer X are also very popular choices. They're basically like heavier more robust versions of the Camper and the Huntsman, except they don't have scale tools (tweezers and toothpick) and they don't have backside tools (hook and corkscrew). An awl also replaces the secondary knife blade and is used in line with the body of the knife, whereas the awl on the Camper and Hiker models is used in a T-handle configuration. A lot of people prefer the inline awl over the T-handle style.
There are other options, but I have listed what I believe are the 4 most popular swiss army knife models for bushcraft. You could pick any one of those 4 models and not go wrong.