Your TV will do a better job of upscaling a 1080p GUI signal to the native resolution of the TV panel (4K) than Kodi will achieve rescaling a 720p or 1080p skin to the same size. Also, unless you have 4K60 media (most people don't) there is not much point forcing the board to support more than 4K30 resolution; it only increases the power draw and heat output of the board. You can still set the whitelist to allow 4K resolutions and Kodi will switch to them when you play 4K media, but then return to the 1080@60 GUI afterwards - the GUI will be snappier at 1080p. This scenario is generally applicable to all ARM devices, nothing that specific to RPi hardware.
You might need to force the Wireless Regulatory Domain for your counrty so the card is using the right radio properties before all frequencies show up correctly. In LE 9.2.3 this will be in the GUI (settings add-on). Until then it requires a conf file setting. e.g.
echo "options cfg80211 ieee80211_regdom=DE” > /storage/.config/modprobe.d/cfg80211.conf
Kodi v19 (LE10) will be entirely Python3, no Python2. It sounds like add-on authors are starting to retool around Py3 which is good.