Xbox One-to-Windows 10 streaming features a "highest quality" setting, there's actually a hidden "very high quality" option available through Microsoft's stream application.
In a post on Reddit, user OomaThurman has discovered that it's possible to unlock an even higher quality setting by modifying the "userconsoledata" file found in the Xbox app folder. By changing the "IsInternalPreview" flag from "false" to "true," you can activate the new higher quality.
Digital Foundry has tested this new setting, noting it "appears to transmit full 1080p imagery." However, the bandwidth requirement could be problematic for some on certain in home Networks.