Hi yes do you know what are RFQ and AGG and the difference between them please as I still haven't got a clue on these 
Can slippage be set low on UniSwap or Pancakeswap because they both have high liquidity and volume hence lower slippage% can be set? I am afraid of setting the slippage to Auto on Uniswap or Pancakeswap because of the Sandwich Hack shown above. Please advise.
For failed tx do funds get immediately returned back to wallet?
I will provide you with this [article] so you can get full details about RFQ and also this [article] to learn about AGG. Can slippage be set low on UniSwap or Pancakeswap because they both have high liquidity and volume hence lower slippage% can be set? I am afraid of setting the slippage to Auto on Uniswap or Pancakeswap because of the Sandwich Hack shown above. Please advise.
For failed tx do funds get immediately returned back to wallet?
To answer your other questions, yes, you can set low slippage on UniSwap or Pancakeswap for highly liquidity tokens; you can set up to 0.5% to execute your transaction.
You're right to avoid the Auto option, as it can actually expose you to a sandwich attack. You can set the appropriate slippage manually and not worry if the transaction fails. The funds will be returned to your wallet, but you will lose the transaction fee for the failed attempt.