Hello as the Subject implicates, I would like to know which is the best online BTC in order to store my BTCs. I know some software wallets like Electrum but I would like to have an online in order to access it from anywhere.
I will assume you already know the risks of using online wallet so I will not go through for warning and security about it.
But if the purpose is only to access from anywhere then use mobile app instead e.g Mycelium, Coinomi, Bitgo etc. There is no assurance that you will be safe at these all the time but it's way better than using exchange app.
There are also exchanges which have a mobile version of their platform. Again if you understand the risks of using it, then it's up to you if you will used them. What are those? Will not mentioned as we aren't sure if you will have a good experienced using them.