[noggin]

can this https://www.amazon.com/INTEL-NUC-Kit-Com...2057441011 and this http://www.ebay.com/itm/ZOTAC-ZBOX-CI327...SwYlRZE0md boot straight into libre-elec and do they have better decoders/better picture quality for all formats including x265 then the odroid c2?

My NUC boots straight to libre-elec yes. It should work fine with x265 yes assuming you have hardware acceleration on.

do you think the hevc or any video format decoder for this is stronger then the video decoder of the Odroid c2?

There should be no difference between the hardware decode performance of MPEG2, H264 or HEVC decoders on any platform - they either work properly or they don't. (There have been occasional bugs in some implementations - including early S905 revisions ISTR)

Where you can get differences in quality is in upscaling, deinterlacing and post-processing.