I'm not really seeing much difference with those small icons, so they're not doing much to explain what you're seeing. Screenshots of an entire game screen would be better, along with a more detailed explanation of what's different.

The method for upscaling in 511 is different than in 510. In 510, upscaling relied on whatever the graphics card preferred; sometimes that was linear and sometimes it was point-based. The latter was unacceptable, as the intended effect was to get a combination of both methods; some graphics cards worked right in this regard, and others didn't. My new system in particular did not upscale in the expected way that my last one did. For this reason, the upscaling was switched from a two-stage method (stage 1 being point upscaling to the nearest integer zoom, stage 2 intended to be a linear scale to the final zoom) to a single shader that got the job done in one pass. I'm actually not sure why your fan speed would have gone up so much, since the shader used to implement this is fairly low-impact.

However, some people decided the "nice upscaling" feature was not entirely for them, and requested a way to change that, so I put one in. In 511 the map control's zoom-mode parameter can be set to normal, distort, or blur. The people who complained about the change mainly preferred the distort mode, which is how 510 behaved on graphics cards (like my new one) that did the final pass with point sampling; when the zoom level is close to an integer, the extra/missing lines of pixels it creates are a little less obvious. Normal mode is the shader, and it's equivalent to how 510 behaved on graphics cards that did linear sampling in the final stage. Blur mode is what a lot of people saw before that in some older versions, where their card just did straight bilinear sampling.

My suggestion would be to talk to the owner of your server and get them to add a menu, similar to the Icons menu in the default BYOND skin, that lets you switch between the zoom modes. That way you can switch to distort or blur if you prefer that. Or, if for some reason your preferred server is forcing distort mode, maybe you'd prefer the normal mode.

There is preference switch--as a skin parameter. But since you probably can't set that directly, it has to be made an option by the authors of that server by adding it to the skin.