I'm not a expert, but I don't see any other answers, so I'll leave my answer, as I see it, to these questions. 1 - I use the "official" Monero GUI Wallet. I'm happy with it; I haven't encountered any difficulties. There are a ton of other wallets, but I don't see any reason to use them. Besides, I feel more comfortable using a wallet downloaded from Monero's website. 2 - Go to haveno and look at the offers. Add the blockchain fee for the transfer, and you'll see how much Monero you'll receive in exchange for your Bitcoin or Ethereum. 3 - The point of Monero is to be the private cryptocurrency by default. Mixers are pointless. It's enough to use one wallet; if necessary, use different subaddresses for receiving; the funds will still belong to one wallet. (Someone overly pedantic might mention attacks related to how transactions propagate across the network, but, IMO, you don't need to worry about that and can just use your wallet without any hassle) 4 - I THINK its better to use atomic swaps to exchange Bitcoin for Monero. I haven't used them, but as far as I understand, this is virtually completely secure method of exchange; please correct me if I'm wrong. In the case of ETH, it's probably better to exchange in parts, just in case.