Pack straps dig into my collarbones after two hours whatever I adjust Gear Question

Packing, most likely, and specifically the shape of the load. A frameless pack transfers weight through its contents, so if the load is soft and slumps there's no column to transfer through and everything lands on your shoulders.

Two changes. Build a virtual frame: foam pad folded flat against the back panel, or your mat rolled into a cylinder around the inside wall, then everything else packed inside that. It sounds fussy and it completely changes how the pack carries.

Then get the dense stuff high and against your back. Food bag and water in the top third, close to your spine, not at the bottom. Frameless packs want a high centre of gravity, which is the opposite of the advice for framed packs, and it's the thing most people get wrong when they switch.

Also, load lifters on a frameless pack do very little. Don't spend time on them.

9kg is around the ceiling for a lot of frameless packs. If that's base weight and you then add four days of food and water, you're at 13-14kg, which is past what most of them do comfortably regardless of technique.

Check strap width against your build. Narrow webbing-style straps on wide shoulders concentrate load exactly where you're describing. It's a fit issue nobody measures because everyone measures torso length and stops there.

One posture thing: are you leaning forward? On a frameless pack with the hip belt doing little, a slight forward lean puts the whole load on the front edge of the shoulder strap. Standing deliberately upright for a minute and seeing whether the pressure moves tells you a lot.