You can worry about tax advantages after you have proven yourself consistent in a world that is nothing short of a deadly jungle. Apologies for gender confusion.
The Russell is illiquid in overnight markets but I'd hardly characterize it as a dangerous instrument due to that - just trade during RTH. It's not a beginner index but it's also less weighed down by the BS of other indices. If ICE were more reasonable with their non pro data fees they'd see more liquidity on it. Commissions are lower than the other exchanges though.
To OP, Trying out to trade ES is fine. The important thing is that you should go sim trade with the amount of money you expected to use, not some random preset $50K offered by the brokerages. Your overall focus on risk control is a good idea but the lack of actual experience trading ES means your approach may not be suitable for you. You need to find your way to deal with the market, and you can do that by experiment with a sim account. Test out trading ideas, techniques and review your results to see what kind of approach is most comfortable for you. From there you will be able to better construct your trading plan and business plan. Good luck!