how exactly do you mount all that stuff?
I have 4 D-rings. One on each side of the waist and one on each shoulder strap.
6' SMB, pre-rigged to a small reel is clipped to my right waist D-ring. If I am carrying a reel for exploration, it is also clipped to the same D-ring. When I'm in horizontal trim, they don't hang down as far as my belly does, so I don't really consider them to be "danglies".
Torch is clipped to my right chest D-ring. I used to have a rubber band (cut from bicycle inner tube) lower on the shoulder strap, to hold the light head. At the moment, I have a tri-slide lower on the shoulder strap with a loop of bungee tied through it and I tuck the head of the torch into that to secure it. I have a matching setup on the left shoulder strap for carrying a backup light.
Wet notes has a bolt snap attached and is clipped to my left waist D-ring and then tucked in behind my waist belt.
EMT shears are in a pouch on my left waist strap, between the D-ring and the buckle. I can position it to be able to reach it with either hand.
DGX Sharp Cut (like an Eezycut Trilobyte) is on my right waist strap between the D-ring and my back plate.
If I carry them, I also have a thin Ti knife and a Ti line cutter hook that go on my right calf and a forearm, held on with bungee loops.
If I'm carrying my GoPro or real camera rig, I have it on a coiled cord lanyard, which I also clip to (usually) my left waist D-ring. It does dangle a bit if it's just clipped off and not in use. But the lanyard has a clip to hold it short when it's not in use, so nothing dangles very far. And it would generally only be dangling like that during my ascent, when I'm no longer worried about danglies hitting or catching on anything.
When I do tech dives, I wear a drysuit with thigh pockets or pocket shorts. I use the pockets to hold a spare mask, a lift bag, and I'll go ahead and stow my wet notes in a pocket, since I only refer to them in an emergency.