It’s quite simple really. The best Tank Race generally would be a Nord and that is due to the resistances you gain. This is the best race for long term progression, it allows you to reach the resistance cap and mitigate damage more easily.
Aside from the Nord the next most beneficial race would just be anything that is sustain related. You would chose a sustain race when you are maybe newer to the game or you’re dealing with specific sustain problems, in this case the Redguard is really good because you get reduced cost abilities and Stamina returned. Imperial is another good option due to all of their cost reduction. Argonian can also be used but you have to use a potion to gain their sustain benefit which might not be good for a beginner player.
Other useful races might include Breton for anyone who likes to play double staff builds or wants additional magicka sustain and they are followed by pretty much every other class which have a varied amount of usefulness for a Tank. The least useful race is a Wood Elf.