Can Ryzen 3 2200g run 4k hevc videos?

Can it run those YES
Can it run smoothly - I suppose it is a question of interpretation of smoothly

not really your chosen one has Vega8

IF you need to go with an APU against a quality separate dedicated card then you need a APU with Vega11
https://gpu.userbenchmark.com/Compa...vs-AMD-RX-Vega-11-Ryzen-iGPU/m441833vsm401440

Yours
http://www.cpu-world.com/CPUs/Zen/AMD-Ryzen 3 2200G.html
as you can see Vega 8

comparison between 8 and 11 in easy to see differences
https://en.wikipedia.org/wiki/List_of_AMD_accelerated_processing_units#"Picasso"_(2019)

and Vega 11
https://www.amd.com/en/products/apu/amd-ryzen-5-3400g

That all said you cannot ever compare integrated graphics with the performance of a good quality dedicated card

and IMHO if you are going to stream 4K videos you will be disappointed

I appreciate that the issue is NOT gaming. However I remain convinced that the

ToxicNinjaOP said:

I especially need 4k hevc (h.265) videos to run smoothly

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requirements are better served by the Vega11 than the Vega 8.
Although the link below deals with the gaming issue, I consider it clearly shows that the need to ensure smoothness will be better met by the Vega11

https://www.game-debate.com/gpu/ind...compare=radeon-rx-vega-8-vs-radeon-rx-vega-11

(Note there are errors on the report, as it references the RX Vega to the Intel processor)

From the report

The Radeon RX Vega 8 and the Radeon RX Vega 11 have the same amount of video memory, but are likely to provide slightly different experiences when displaying game textures at high resolutions.

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The RX Vega 11 has 51.2 GB/sec greater memory bandwidth than the RX Vega 8, which means that the memory performance of the RX Vega11 is much better than the RX8

Also

The Radeon RX Vega 8 has 1280 Shader Processing Units and the Radeon RX Vega 11 has 1536. However, the actual shader performance of the RX Vega8 is 841 and the actual shader performance of the RX Vega11 is 1188. The RX Vega11 having 347 better shader performance and an altogether better performance when taking into account other relevant data means that the RX Vega11 delivers a significantly smoother and more efficient experience when processing graphical data than the RX Vega8.

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I do appreciate as I said that the issue is not gaming, but the streamed video must still be processed by the GPU and I am, as I said convinced you will find the 11 better.

Although this link is from an article now 2 years old, you can read all about it here
https://www.reddit.com/r/hardware/comments/66ovx4
ToxicNinjaOP
I have provided you with quite an amount of linked content and I am of the firm opinion you would be better with the VEGA11 graphics
That said you now have two opinions
I would advise you, unless someone else replies to seek the opinion of AMD stressing to them your requirements.
Also of course although you did not ask, please remember that a VITAL aspect is the quality of your network - connection from the aspect of bandwidth