I found the following site to compare camera sensor noise levels.
https://www.photonstophotos.net/
Click on “Input-referred Read Noise Chart” to compare read noise at different ISO for different cameras. The advice I read was to pick the highest ISO where the curve flattens but do not go into the triangle area.
I am not an imager but my son is interested in having a go. I have a Canon 40D and 5D Mark II to practise with. Looking at the noise charts there are better cameras but looking at older photos on this and other web sites it appears those cameras are more than adequate. Neither is modified. Canon 50D for some reason is not listed. 60D and up have the flip mirror.
I was always Nikon film SLR user but with digital went for used Canon which with an adaptor takes my manual Nikkor lenses.