Setting zero cache is strongly ill-advised and I'm not a fan of using SD cards to cache content. Better use my 16GB internal storage. It will be years before the internal storage faces any read or write issues and by then, most of us would have moved on to a better box. So no worries there. I manually set cache size to around 200MB-ish & it's proven sufficient. Remember that the higher the cache size you set, KODI will need around 3 times that as RAM. So make sure your box also has sufficient RAM as well to avoid issues.

hi, i am using it right now. so far so good. no issue. most of the time watching kodi, MoviesHD and CartoonHD. Watching downloaded MKV movies also no issues .

IMHO, If you can upgrade to a 2GB RAM equipped box, do so. Then you can increase the cache size should you run into buffering issues that shouldn't normally occur. About the M8s Amlogic S812 box, guess you've gotten real user feedback on it.

i use asus, rm200 (now maybe rm250 due to weak rm). excellent for ethernet and wifi.
forget the unifi stock router which is ok for basic use, small space.
no.
unifi 30 will not do more in kodi.
kodi buffering is usually due to geoblocks, bad links or unsupported chipset.
vip10 has enough speed for everything if single user.
higher speed is necessary if u have multi users at any one time.
incl torrenting.
but, since unifi30 now is same price as old vip10, might as well change unless u need the upload speed.