when enabled, i can still resize the window and that should not be possible. because it gets resized accidentally.

yes as a mouse racer this is true, it can still grab a 1pixel boarder around the window, hence resizing.

this will always be the case i think, so in the end if you want to race with a mouse, race full screen... and flick between full screen to window using shift F4, if you ever feel the need to go back to a window to do something else.

there's no 'in the end'. this is something that needs fixing. it will propably be one of the last things in Scawen's 'to do' list right now. but i expect he will correct it, in the next patch and from then on the issue will be gone.