For others to help, u gotta tell more about what u have...

Internet speed, router, what other devices, what u like, etc.

u have a problem with wifi then...

.. router upstairs, tv downstairs is a bad arrangement, more so if router is at a dead corner spot or the tv is.
.. asus "UHP"... likely rtn12uhp - this is a few years old, N router (can't do ac 5 ghz), max 100mbps.
good router no doubt but difficult to do the job u need.
either u lay LAN cable which is a shit idea for most or u spend money to get a MESH network - Asus AiMesh or TP link Deco D5 or D9.
short of that, i suspect the most u get from the 300mbps is 10mbps, which explains why even netflix doesn't look good.
u can try with a better single router like AC86U or AC88U but hard to say if it will work well in yr case.

.. chinese dramas - try these:
http://www.mediafire.com/file/885170z6yvrs...TV_100.apk/file
https://apkpure.com/adrama/alphastudio.adrama
download and sideload on TV like u did with unifi@playtv.

movies/sports/tv shows... yr best bet is unifi@playtv and astrogo which are legit.
there are other ahem apps that can do but i do not wish to discuss here.

i am using this router... 2x2, quite good with 5ghz if distance not too far, not too many obstacles.

from one corner at one level to diagonal corner at another, that will be the worst... may get <10mbps.

u can test it with ookla app on phone tablet or the tv itself.

besides changing to 3x3 router or mesh routers, u can also try using another AC router as repeater, connect to TV with cable - this, maybe can get 30-50mbps.

diff apps may give diff results.

it is also possible the wifi module of tv 2.4ghz is not so good.

i have another tv at a rather dead spot... can barely get enough wifi to work on netflix.

now using a repeater, 30mbps is good enough for just about all apps.

any router that has repeater mode will do.

most AC routers have this mode, only the cheapest ones don't.

if u can, find an old router to try first.

still, u need to find a decent spot for the repeater to get fair reception, yet not too far for cat5e/cat6 cable to connect to tv.