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?
It depends on the platform you believe provides the perfect information you need for the Bitcoin transaction.
For BTC one the most platform people always use are:
mempool.space for fee estimates, and mempool stats visualization.
blockstream.info for transaction confirmation stats and privacy.
blockchair.com is good if you want check transaction stats, memepool for many blockchain, also have advanced filters/search, etc.
blockexplorer.com can be use to check latest block, broadcast TX, etc.
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?
For Ethereum, etherscan.io is still the best and it's memepool is etherscan.io/txsPending ,
https://blockchair.com/ethereum/mempoolSolana is solscan.io or explorer.solana.com
Tron is tronscan.org. You can also use okx.com/explorer for options