always make use of those various ways on mixing up your coins on deleting or erasing up your trails but we know that it is already that hard to trace up when you do
make out transactions in between wallet to wallet or from exchange into your personal wallet or vice versa.
Withdraw your coins from exchanges, move it to another wallet of yourself or move it to another exchange then to another wallet of yours is good enough.
Or move bitcoin to an exchange, trade it to Monero, withdraw Monero and move Monero to another exchange to sell it to bitcoin. Withdraw it again. You don't need to use Mixers if you are ready to do some steps by yourself.
https://kycnot.me/If you are lazy, use mixers is good enough and more convenient.
I think it depends vary from person to person . What kind of security he needs depends on whether he's going to be using a mixer because if it's not that important I think mixing is a waste of money.
Using mixer does not increase your security but privacy and anonymity.
Make sense, if they just deposit the Bitcoin to another exchange, I don't think a Bitcoin mixer is still needed here. I believe it will different for every different goal of the person. If they are sensitive about privacy, for sure they will do such things as this.
And there are also some Bitcoin mixers are not to be trusted because maybe instead you will become safe, your funds will indeed be frozen or get scammed or being linked to other Bitcoins that is identified as fraud.
Exchanges do batch transactions in outputs for user withdrawal requests. They are like a mixer for users already and they are used by some people to do money laundering too. Same for money laundering on cryptocurrency gambling sites. If you simply make deposit then withdraw your coins on exchanges or gambling sites, it can be one of factors for them to investigate your accounts for potential money laundering.