All scams. A CPU Is a CPU. There's nothing a phone CPU can do that a PC CPU can't do better. "Phone only mining" is a pure lie.
Not all of them. Magi has a unique PoW algorithm (M7M) where it punishes big miners, instead of the "little guy". The higher the hashrate, the lower the block reward will be. This makes it easier for anyone to mine XMG on mobile devices. The only downside is that the number of exchanges are low (as well as market price).
Bad example.
M7M is a regular POW algorithm, there's nothing mobile about it, It can be mined with any desktop, laptop, workstation or server CPU.
If anyone claims M7M is mobile only they are scammers. My previous statement stands, all mobile only mining is a scam.