Back in 80s when Look 1st came out with their pedals , Black “fixed” was all there was. Many still like them the best . I myself am back on 0 degree cleats because I feel knee stress on my right knee that had been thru some trauma from a few accidents not related to cycling. Keep in mind I’m one of the cyclists that had a solid position when riding with Fit Kit meaning my feet/knee/ankles did NOT move at all with all the free swiveling in that patented tools range, telling fitter I have a super still biomechanics)So this doesn’t mean floating cleats are bad for every rider, however all riders can try fixed and see how their knees feel, there is no definite answer here in this blog, you won;t know till you try.
One good useful thing about fixed cleats, wether you stick with them or not is you can find your absolute zero position for cleat angle, THEN pencil or ink mark that angle good (with straight rod of phillips screwdriver) when you are cetrtain the ideal angular setting is achived, so after that you decide if you want to keep them on, OR remove to re install the floar cleats that will now be set in the ideal angle so you get the best biomechanics with ANY variation of Look type float cleats. which at that point are more likely to allow better pedaling dynamics when your fine tuned body can keep feet more centered with minimal movement, UNLIKE when the cleats are installed at a sloppy angle, WAY off from that zero position point angle.
Last thought for all of you serious riders seeking optimum, is if there are local shops with that classic cleat fitting tool (FIT KIT) in your area, and you can set that up witin pandemic restrrictions, then try that out, it may be just what you need to get the best cleat fit ever, and from there you can really give the 0 degree cleats a trial, Good luck all of you and God Bless you