These are some WIFI-TV system reviews that may help understand your choices:

The best streaming devices for 2019 - Digital Trends
Link: https://www.digitaltrends.com/home-theater/best-streaming-devices/

The Best Media Streaming Devices for 2019 - PC Magazine
Who needs cable? We pit the highest-rated streaming boxes and sticks against one another to find out which one is your best bet for watching shows, movies, and more on your television.
Link: https://www.pcmag.com/article2/0,2817,2421457,00.asp

and,
The 12 Best Devices to Buy in 2019 for Streaming TV - Life Wire
Cut cords with the cable companies and stream your content to your TV
Link: https://www.lifewire.com/best-devices-to-buy-for-streaming-tv-4061016

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Here are some links to the equipment supplier's web sites (there may be others):

1. Roku: https://www.roku.com/how-it-works

2. Amazon (Fire TV): https://www.amazon.com/b/ref=d_devcp_smp_img/ref=s9_acss_bw_cg_deviceCP_2c1_w?ie=UTF8&node=8521791011&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=merchandised-search-top-2&pf_rd_r=75140YPH3ZGY5DQDT1ZQ&pf_rd_t=101&pf_rd_p=12532529-74fe-4b68-8961-93cf88d8719a&pf_rd_i=2102313011

3. Google Chromecast TV: https://store.google.com/product/chromecast

4. Apple TV: https://www.apple.com/tv/

5. Nvidia Shield: https://www.nvidia.com/en-us/shield/

Most of these boxes can be bought either directly from the manufacturer or from web stores such as Amazon, Best Buy, etc.

This all gets very confusing to me. Please understand the difference between the streaming receiver boxes (Roku, Fire TV, etc.) and the optional subscription content providers (Netflix, Hulu, etc.). You buy the box first with their FREE content, then subscribe to optional content if you desire.....somewhat like basic cable TV and their optional entertainment/sports packages.

Good luck!.........