@DavidP is correct. The truss rod is not for changing action. Action and relief are not the same.
If you want you guitar to play it’s best, set the relief first. Then use the saddles and, if necessary, the nut, to set action.
The saddle sets action all along the fretboard. Not just the higher frets. If the nut is correct, that end will take care of itself. If the nut is not correct, nothing will help it except fixing the nut.
The relief is the curve of the middle of the fretboard. It can be flat, curve back (back bow, where the head is lower than the body), or curve up (where the head is higher than the body). Important is that the portion of the neck IN the guitar body does not bend.
Strings pull the neck up (head up, forward bow) to different degrees depending on string tension. Higher tension pulls harder. Changing strings to a higher tension may increase relief, lower tension may decrease it, potentially even causing back bow.
In my experience on my guitar, one step in gauge makes negligible difference, but greater than that requires truss adjustment. Your guitar may be different.
If the relief is too low, you may need to raise the action to avoid buzz, and the action at the high frets will be too much and the guitar will play poorly.
If the relief is too much, and you lower the saddles to set the action where you want, you will find that the middle of the neck has higher action than the two ends. This may be ok, so isn’t necessarily a problem, but can affect intonation and playability.
If you set the relief to reasonable recommended height, then set the action where you want it, it will work the best.