There is such thing in “Display Options” under the “Render” tab as “Image View Resolution”.
But whatever I do with it I don't see any effect.
Is it supposed to work? If yes what is the correct usage?

There's a viewport type called “Image” in the LOPs Scene Viewer (type as in Persp, Top, Front, etc). It will attempt to get the resolution from the current Render Settings Prim first (see in Persp menu, Render Settings submenu). If that does not exist, it uses this resolution to render the image. This resolution and the Render Settings prim resolution have no effect in the other 3D views.

this view does not work with openGL. only with a live rendering from a render engine. its bare bone and so laggy, it un-usable.
but i didn't try it on lastest build.

schwungsau
this view does not work with openGL. only with a live rendering from a render engine. its bare bone and so laggy, it un-usable.
but i didn't try it on lastest build.

It's very much a work in progress for 18.0. It'll eventually become much like the Render View.

It's not laggy on the latest build, but it's still barely usable. The most immediate issue now is that there doesn't seem to be a way to adjust the zoom level relative to the buffer size. It is always relative to the pane size. It would hold things over a little bit to be able to set the zoom level to 1-to-1 or other integer scaling levels.

twod
It's very much a work in progress for 18.0. It'll eventually become much like the Render View.

right, i hope for the next version we will get more “render tools” ?