This is my personal preference from my experience and what works for me - it may not work for you - so take it for what it's worth.
The lanyard you listed is a good choice and will keep your computer close to you - yet allow you to detach if need be. However, I find a ss bolt snap is much more simple and will last a lifetime.
For the octo, I prefer a necklace as shown here or w/ bungee:
Manta Regulator Necklace, DIR and Technical, Manta, Manta Regulator Necklace
This keeps your octo secured the same place every time. Just remember you donate your primary, so it should be on a longer hose to make for a safer air-share if need be.
Keep in mind this is just what works best for me - others will chime in what works for them.