First of all, I'm sorry i don't understand french but i think i understand your question :)

I'm not 100% sure if Digitec really stated the correct SoC Specification.
"Mobiler Prozessor: Qualcomm Snapdragon 450"
There is a much higher probability that this device is using an Exynos 7904 SoC and not a Snapdragon 450.

- Samsung Galaxy Tab A 10.1 (2019)
Qualcomm Snapdragon 450 / Adreno 506

*Hardware-accelerated Videoplayback:
Resolution: up to 1080p/60fps
Codec: h264/AVC & x265/HEVC

H.265/HEVC hardware-decoding is supported but be aware that this doesn't include H.265/HEVC 10bit.
Officially Snapdragon 450 SoC doesn't have Hardware-accelerated Video playback for VP8 & VP9 but a couple of people on the web stated that it does. So take the VP8 & VP9 support statement with a grain of salt.


- FYI: If you need Hardware-accelerated Video playback for H.265/HEVC 10-bit including VP8 & VP9 (with VP9 10-bit) then you should look out for Qualcomm's Snapdragon 800 Series.

Starting from Snapdragon 820 & 821 there is Video playback support for up to 4K/60fps supporting all the codecs i just mentioned.
From Snapdragon 835 they added additionally HDR10 support.
From Snapdragon 845 & 850 they added additionally HLG & BT.2020 support (inofficially H.264 10 bit support)
From Snapdragon 855/855+ they added additionally HDR10+ support and boosted the Video playback resolution to 8K/30fps

btw a cheaper alternative from Qualcomm might be the new Snapdragon 720G.
It supports Hardware-accelerated Video playback for H.264/AVC, H.265/HEVC (including HLG & HDR10), VP8 & VP9


But let's say Digitec really made a mistake and they are selling the Samsung Galaxy Tab A 10.1 (2019) with Exynos 7904 Soc.
Then the following information would be good to know ;)

- Samsung Galaxy Tab A 10.1 (2019)
Exynos 7904 / Mali-G71 MP2
Resolution: up to 4K/30fps
Video Encoding and Decoding: H.265/HEVC, H.264/AVC, VP8
Video Decoding: H.265/HEVC, H.264/AVC, VP8 and VP9

Officially Exynos 7904 (Mali-G71 MP2) doesn't support HEVC Main 10 (10 bit) Video encoding.

Hope this helps in some way :)