[moltuae]

You could also look at the Trezor hardware wallet. I haven't got one yet (it's on my 'to do' list though) but I know a few people who use them.

Hash-rate is a measure of performance of the hardware so it shouldn't change with difficulty. I'm not familiar with ethermine.org though. It's possible they calculate a relative/effective hash-rate.

The best coins to mine aren't necessarily the higher value coins or the ones with the greater market cap (I tend to use this site for comparison: https://coinmarketcap.com ). In fact, often a newer coin can be more profitable, if the price is high relative to mining difficulty. This site is good for comparing mining profitability: https://whattomine.com

I went down that mining route a little myself initially then I got lazy and just started using NiceHash instead. The problem with mining individual coins is that you need to spend a lot of time monitoring profitability and switching between different coins. If you're prepared to do that you can probably make a little more profit than you can by using NiceHash, but you'll have earned it. Having said that, it can be fun mining different coins and pools, and it could prove profitable if you pick a promising new coin.

You could also consider 'staking'. Some coins are generated by Proof of Stake (PoS) rather than Proof of Work (PoW, aka mining), and some use a combination of both PoS and PoW. With PoS you earn new coins just by holding (and sometimes 'locking') coins in a wallet.