You can try and guesstimate what’s happening by trying this:
-Generate some test bars in Premiere. New item – HD bars and tone.
-Check out how it looks with all the Lumetri scopes visible. It should look pretty clean and the vectorscope zigzags through all the colours.
-Render the bars out in the formats you want to test.
-Bring the exported clips back and compare them to each other and the original generated bars.
You should see some differences. Depending on the bit depth/chroma subsampling/other stuff there’s probably noticable differences in the brightest saturated areas. Also the brightly saturated areas might be blending into each other a little bit so there’s no clean line like in the generated version.