There may be a bunch of conflicting information out there because symmetry issues can be complicated. For example: https://www.stevehoggbikefitting.com...ole-of-a-shim/ One side could be longer than the other, but also it seems in some cases one side compensates to protect the other.

So, correctly diagnosing via internet is impossible. There are some things I would be thinking of doing:

1) test out a slightly lower saddle position (5mm lower) just to see if it helps. Posterior knee pain may demand a lower saddle height. This idea is based on your right posterior knee discomfort, but it may also play into your other issues. Keep a record of current saddle height.

2) consider shimming cleats, probably on the right side but if that makes it worse try the left (as above link suggests, this can be complicated)... this assumes you are riding clipless pedals

3) work on your issues with stretches and strengthening exercises. For example, gently stretch the piriformis and strengthen the gluteus medius (no gym equipment required). Try checking if your hamstrings right and left have similar flexibility (lie on back on floor, bend hips to 90 degrees, straighten knees as far as possible.. have someone help gently if possible... are left and right similar?)

4) see what happens if you consciously place and keep your left and right hands stay in symmetrical positions during a ride (other than when shifting).. you may be supporting more weight on one side.

5) look in the mirror for any asymmetries: are your shoulders the same height? do your hands both hang down equal distances from the ground when you stand and let your arms dangle? are your iliac crests both at the same height (measure them against a doorway if needed). The idea here is to see if there are any really obvious asymmetries.

You may also find this interesting as the first part of it talks about asymmetries: https://www.stevehoggbikefitting.com...ght-side-bias/