Keep all coins online is dangerous. Even the most trusted exchanges can be hacked or closed. If you are an active trader, keep the needed amount at the exchange, but all "inactive" coins should be at wallet.
If you plan to make a long-term investment these restrictions will not affect you in any way. The company needs time to develop and launch the product, after which the token's price will begin to grow.
Even MyEtherwallet site says "Entering your private key on a website dangerous. If our website is compromised or you accidentally visit a different website, your funds will be stolen." So, if you want an additional security, use MetaMask separately or in conjunction with MEW.
I would say Monero. Its technology aims to pick up where Bitcoin left off and even doesn’t work (i.e. non-ASIC mining, anonymity). Team is a leader in the industry and will be one to watch indefinitely.