FWIW, I've never had a bike fit. I just started riding and reading up here and there.
The keys that I have found are...
Seat height placement (i.e. forward or back) and angle
Cleat angle.

IIRC, they used to call Lance Armstrong Mister Millimeter because he would make changes very incrementally. Whenever I adjust my saddle height, I do it in 1 or 2 mm increments. If I don't feel like I am getting good extension (like sitting in a kitchen chair lifting your feet up and down) then I will take the seat post up a couple of millimeters and go for a ride. Eventually I get to the point where I can just feel that I am overextending my legs and I dial it back.

I once bought some 0 degree cleats. I used them for a couple of weeks and they killed my knees. Some people have a nice straight pedaling gait where the angle of their feet with regards to the pedal changes very little. I am not in that group so I like cleats with more angular motion. 6 degree typically.

Although a standard fitting will suit most people, not all people are built the same.

Measure your current fitting very accurately and don't be afraid to tweak it a bit here and there. Eventually you will find your comfort spots.

Not trying to derail, but in regards to GCN videos, are they considered to be reliable to give 'pro' technique examples? I watch their vids from time to time and they come across as 'extremely interested' enthiusiasts. No offence intended.

Spinay70

Are there no books on cycling technique?

This is very personal and anecdotal............but I feel like I improved a lot after I had begun to do really hard intervals in the 3 minute or so range. Enough duration that you're not racking around sprinting, but enough intensity and duration that your body is going to really really really want to find the most efficient pedaling to cope with the work load. That also goes to say that during those efforts your body is going to want a nicely setup bike too in terms of fit. That's how I figured out some cleat position tweaks.

Just me. May seem odd, but seems the that kind of stress forced me to get it "correct" for my body.

A couple of thoughts ...

1) IMO, one thing that minimizes knee stress is to move one's knees straight up and down directly over the feet. For some people, that's brushing the paint. For others, like me, it means installing peal extenders. I was having knee pain for a few years. Since I installed the extenders last year, my knees go up and down directly over my pedals (pinned flats), and my pain is virtually non-existent - but YMWV.

2) I don't know what you mean by 'rocking your hips.' I think people are talking about bending forward using your hips as the hinge, which keeps your back pretty much oriented the way it is when you're standing or sitting straight. Not bending your back helps the vertebrae and discs, I believe.

No offense taken, I have no vested interest on their video productions.

I posted them for a couple of reasons. First, I personally found these videos to be helpful. Second, I wanted the OP to get a different take on some of the other advice given here. And three (OK that’s more than a couple of reasons) I wanted to showcase (or show off) one of the roads that I regularly ride.

Also riding fix gear. My first season of racing (in a distant millenium) the vets in my club told me to set my second bike up fix gear to learn to pedal smooth circles. It works really well (as long as you keep your gear low). Ride hills, both for the grunt workout going up and the ridiculous spin coming down. That spin is where you really learn. Until you have taught your leg muscles to completely relax, fast downhills are about as much fun as bronco riding on a jackhammer. But keep practicing. The day will come when you can pedal 40 downhill in a 42-17 (200 rpm). You will be pedaling perfect 100 rpm strokes on the flat. And you will have leg muscles that have learned to relax all the time they are not actually involve in the power portion of the stroke. Actually recovering while you pedal.

Now, don't get all dreamy about this - fix gear riding is hard work, on average 25-33% harder than the same ride with gears and often still not as fast. (Great in the winter. More benefit from shorter rides. Downhill are a lot warmer because you have to work.) Of course, there is the danger (?) that you will take to fix gear riding like some of us have. It can be addicting. And, set your fix gear up with good brakes. The point is to work on pedal style, not hipster showmanship. Braking with your legs to go downhill is exactly the wrong thing to be doing for your pedaling form. Spinning too fast to even think about braking with your legs is where you get the benefit. Get the good brakes so the EMS doesn't have to extract you from a tree.

Edit: Do you have only one bike? This might be a great time to find a local coop, buy a 1980s bike with horizontal dropouts and with their help, set it up as a fix gear. There are many suitable bikes out there. All the Japanese companies had models that work very well. Likewise Trek, the French bikes (but you may need the coop expertise there), many Raleigh s, etc. Bring your current bike along so you can purchase a bike you can set up with the same contact points (seat, handlebars and brake lever locations).

Ben (who's had and been riding at least one fix gear continuously since 1976)

Perfect

Thank you all for the replies. I have been trying the scraping the top tube with your knees and high cadence.

I have found a great improvement in my knee comfort. I will keep you all updated over the coming months.