I do wear an inflatable pfd with a harness, at all times.
I use that tether, I like a quick release. I had one fail and WM replaced it for free.
The Spinlock Deckvest is very popular, but not approved. It uses a cow hitch to attach the tether, but the vest has a built-in cutter. It has thigh straps. I have added a crotch strap to my pfd.
I have the same setup. When off shore as part of a crew or alone I wear the spinlock integrated PFD, with harness with a plb attached. The crotch straps are never in the way and a great addition. To me wearing a pfd with integrated harness is the way to go and you dont even know the harness is there. I never pay retail for any of this stuff and have accumulated them over the years, At the boat show last year Annapolis performance sailing was 40% of their pfd, teathers, and harnesses.
I do a lot of single handing also, If it is to become part of your routine, I would invest in some quality stuff and accumulate it over the years as it can be expensive and you can wait till they have deep sales on them. The harness you are looking at is adequate, but could really cut into you you if you really had to use it, Also the quick releases are important that they are qualoity and will work when called upon, not just to move from jackline to jackline, but in an emergency under adverse situatuions and pressure on the clip.
Staying on the boat is the first priority of course and your safety equipment/ system should be first rate to save you, not an afterthough or just sale priced.
Here is my single harness- very lightweight and great construction
Spinlock Deckware - Deck Pro Harness: Mauri Pro Sailing
It doesnt cut into you when you wear it for long times like the webbing harnesses will.
Spinlock Deckvest 5D 170N Pro Sensor Inflatable PFD & Harness
ACR 2881 ResQLink+ PLB Personal Locator Beacon
In the bay I usually wear an integrated Mustang with harness when single handing.
Mustang MD3184 PFD Auto Hydrostatic Inflatable-MD3184 Mustang
Check out the teathers on here. I have this one
Annapolis Performance Sailing (APS) - Race Safety Line: Cow Hitch + 2 Clips
Generally I run a jackline from the cockpit to the mast and a second one to the bow.
Inflatable PFDs | Hydrostatic, Manual, Automatic | Spinlock, Mustang - Annapolis Performance Sailing (APS)