Thanks all for reply.

Security is not my main concern because I always keep my pc and phone protected with anti virus and as a tech guy i am aware of it.

1) My main concern is , I like online wallet like bitcoin.com, trustwallet  etc.. where they provide private keys and 12 words secret phases. Can they have still have custody of my coins anyhow? Is coins stored on their server?

2) In hardware wallet, does coins are stored in hardware? or only private is stored in a hardware wallet? Eg. suppose if there is 0.1 BTC in our wallet it is stored in address and can be seen in blockchain ledger so actually coins are stored in wallet address on blockchain server and not on hadware or software wallet. Am i right? or not?