Mining is profitable only if you use a computer you don't pay electricity for. If you running your own devices, it's not worth it.
If you are using a computer that is turned on anyway running the mining in the background can be profitable with fairly cheap electricity cost. Use a hardware monitor like
https://www.hwinfo.com/ to measure how much extra electricity your CPU uses when mining and calculate the value of what is mined and find out if it works for you.
I'm pretty confused about people talking about house edge increasing or decreasing here.
I thought I had explained that above. Using a martingale means that your average winning bet is smaller than your average losing bet. It can be mathematically demonstrated that the -EV increases the longer you play. You can't decrease the house edge.
The more you bet, the more edge you give up.
If by 'the more you bet' you mean the number of bets then the larger the number of bets the less variance of luck and therefore the closer the expected outcome will be to the house edge.
How you bet doesn't matter. If you want to give up the lowest edge while having a chance to win something decent, do small bets with small odds to win.
Lots of small bets will have less variance and the result will trend towards the house edge the longer you continue. A smaller number of large bets will have more variance so you have an opportunity to have good luck and come out winning.