I've just bought an Xiaomi Mi stick and installed Kodi on it. I'm trying to stream my movies from my NAS but ever 10 seconds or so it needs to buffer. I've tried to connect through both 2.4 GHz and 5 GHz but they both work bad. It's not problem to stream the same mcoies through wifi on my computer. In my living room I have an Nvidia shield at that works great, also through wifi. Is the Mi stick too slow for Kodi and 1080p movies?
If you want Kodi's functionality, but in a more lightweight form then try out Stremio. Honestly, for me it's way better than Kodi since I don't have to deal with any stupid issues anymore. Less of a headache. I wrote about it here.
https://www.juststream.io/stremio/