it's not important to know how they save their Bitcoin, because even if you know it, it doesn't affect anything in your life or the value of your asset if used the same way with them. Maybe it will increase your doubt to keep hold of your asset if you know they saved it in exchange and felt they were on guard if the market does not meet their expectations. So, if I were you, I would believe in myself, and not use the wrong way the same with the institutional. Because they have a business target, and must take action immediately to sell their asset if the market crashes suddenly. So if they keep their asset on a non-custody wallet, or with the multi-signature way which is quite complicated to take action