Hi!
Is there a way to disable Z-Buffer? Profiling shows huge amount of resources in PosOnlyOpaque. I tried r.EarlyZPass 0 but has no effect in ms
Z-Buffer and Early Z pass are different things. Assuming you are referring to latter one, you can disable Early Z Pass in project settings, but there are certain features, that will force Early Z pass on, even if it is disabled, such as forward shading and dbuffer decals.
On a side note, position only shader is exceptionally fast, and if you are getting slow pre-pass, quite likely you are doing something wrong.