I know there are many sites out there when you can either enter a bitcoin address or transaction id and get more information on it. Such as you can check for confirmations and all of that. What is the best site for this? Is it blockchain or blockchair or something else? I heard of blockexplorer as well?
What about when it comes to other coins like Ethereum or any other coins? For Ethereum, is it Etherscan.io? What about mempool? Are these sites all legit?
You have years of creating many threads with basic questions, even repeatedly asking same questions and now you are asking about very basic questions about block explorers.

I guess he's pretending to be stupid, I'm not sure an account created almost a decade ago is still asking questions like a newbie.
This user have habit of re-asking similar question every few months-years. Please check reference link for additional information.
This guy has been posting the same questions over and over again for many years. Don't waste your time on him, there's no point.
Just click Ignore, that's what I did.
creates multiple topics and posts in short time span