Question About Transactions and Miners

[Awesomus Maximus]

Trying to understand the mining process, I encountered several questions regarding mining and transactions.

I understand that the miners get to chose (or rather their software) what transactions they will include in the next block. I also understand that the transactions with higher fees will have higher probability to be included first. But then:

a) Isn't it so that each miner has its own version of the next block to be added to the chain?

b) Where and how does the miner draw the line, and decides no more transactions (low fees) are allowed in?

c) Will the miner who makes the decision quickly, and say, decide to mine a block half-empty gain advantage over other miners by starting the race sooner?

d) Has anyone an estimate of the current average sum of transaction fees per block, in addition to the 12.5 BTC?

It could be that all these question have been answered before, but I couldn't find any satisfactory answer.

[Awesomus Maximus]

No hints?

[kangbasir]

I think the difference between objects Transactions are implied the same because both obtained by mining or mining one way to get Bitcoin. As mentioned earlier, we can see Bitcoin as a large global cash system that stores transaction history BTC

[keping1]

too many must be known to be a miner of my advice you can learn the same miners by investing your funds while you learn to mine with them.

[Awesomus Maximus]

Thank you all for taking the time to reply, not exactly the answers I've been looking for though.