If you wore hard lenses the quality of soft lenses would be a disappointment anyway and would not be a choice. I have keratoconus, so specticals are not a choice. After cataract surgery, corneas were distorted, but smoothed out by soft lenses and vision corrected by hard lenses.
I'll probably need cataract surgery within the next decade; my ophthalmologist has me on "wait and watch" while recommending I minimize UV exposure (not a big problem, as I can't order glasses lenses without 100% UV coating even if I wanted them). Apparently, cataract surgery now includes a near-mandatory Lasik surgery to finalize the vision over the implanted replacement lens, and I'm not looking forward to convincing the docs to leave me nearsighted (I'd rather wear glasses every day than have to deal with magnifiers for close work like camera shutter repairs) and keep the two eyes about the same (they like to "eliminate bifocals" by making one eye focus for distance, the other for reading). I refuse to give up my one piddly little super power, my built-in microscope.
Sure do wish the FDA would approve those drops that reverse cataracts...
With Kiev viewfinder first watch for sharp edges around opening. It's deadly for plastic lenses. I wear spectacles all the time and refuse to fit it with anything but glass lenses. It's getting harder to find shop to deal with glass. Also It's very hard to see edges of the frame thru that viewfinder, so additional one on accessory shoe is good idea. USSR turret one is very nice for me. So bad that Kodak Retina auxiliary viewfinder has just 35 and 80mm lens option. You will be fine with RF patch as long as you protest your lenses from scratching.
Within my budget, glass lenses are simply impossible. I buy my glasses online, get bifocals for WAY under $100, vs. $600+ for a pair bought from the eye doctor's optician -- but even the specialists can't/won't produce glass lenses in the -6.75 range; they'd be too heavy and too thick compared to high-index plastics.
I just tried looking through a Soviet Era shoe mount Turrentine viewfinder with my classes on, and it is usable. Not ideal, but not bad. I have come to the realization that I shoot with my glasses off, and view the world with them on, but I see perfectly close up, and badly at distance. And my eye doctors have been unable to come up with a prescription that works both at distance and closeup.
If you're past your mid-40s in age, that's not too surprising. The best you can get is a compromise, even with bifocals. I order my glasses online, from Zenni Optical; this last time around I ordered one pair of single vision with my distance prescription, and a second pair with a reading prescription (+1.25 diopter from the distance prescription) and bifocals (giving an additional +1.25, so a focus around 10 inches as opposed to roughly arm's length). Much more useful with the close work I do every day repairing power tools. Two frames and two pair of lenses, one pir bifocals, and the total bill was around $70.