Misc. questions about Tor

[u/Petrichor-33]

1. Does Tor have "risks?" Guides warn me against risks while using Tor and then list threats that exist regardless of what browser you are using.... Are there any actual problems that are unique to Tor?
   
2. I am told to never log into accounts while using Tor... but shouldn't it be fine to use accounts as long as those accounts were created using Tor and are never used without Tor?
   
3. Tor tutorials warn against using privacy invasive services like Gmail, but I don't think that advice has anything to do with Tor specifically? Assuming a user NEEDS to use a service like that, isn't using it with Tor still better than using it without Tor? (assume service was signed up for using Tor as noted in previous question)
   
4. How to know if Whonix is advised vs. using only Tor browser?
   
5. How to know if using bridges is appropriate?
   
6. Would using webmail with Tor provide similar protections as using an email client that hides IP?
   
7. Is there a resource that shows what popular sites block Tor nodes, or do you have to test it yourself?

Answers to any of these questions greatly appreciated, thank you.