Hi, implementing GLSL checkbox, OffScreenRenderingMode dropdown menu and VideoMemorySize textbox into winecfg would be easy.
GLSL is OK IMO, because some drivers(*cough* macos *cough*) have serious problems with glsl. It could be included into the shader dropdown box. The issue that needs to be dealt with is that we can't combine arb vertex shaders and glsl pixel shaders or vice versa.
Video memory size maybe too. There are vendor dependent ways to read it, but implementing them is pretty nasty(requires some private to winex11.drv). Altough we had that discussion a number of times already and we only agreed on a registry key so far.
Offscreen rendering should have fbos fixed and made default, otherwise use backbuffer(not pbuffer because backbuffer with aux buffers is cheaper). I don't think it is a good idea to add it to winecfg
I don't think render target locking should be configureable as is. That rendering should be fixed to catch NOP locks some games do(which does the same as glFinish() on windows).
What I have considered is some performance vs correctness slider. With decreased correctness things like render target locking or drawStridedSlow are disabled. If the correctness is decreased even more some properly implemented, but known to be expensive settings could be deactivated, like smooth shading, per pixel fog(ok. not sure if that is expensive). Windows drivers have such a setting, so why shouldn't we :-) . This slider could also cover some software emulated features like vertex blending(if we ever get that). Of course we shouldn't pollute the wined3d code with if(someSetting) statements either.