99% payout is very good, but $3 per 1,000 isn't the best if you end up taking liquidity on lots of trades, since that can add up fast on 1M shares/month.
Riskparity: although T3 may have "high rates and fees" it's different if you go through a sub, as DT3 mentioned, subs are "Class B" members and can negotiate their own rates/fees. WTS traders, from my understanding, have a two-year lock on their rates, so it's probably a good idea to go through a sub rather than directly going to T3.
Other licensed prop firms to look at:
Avatar Securities
Chimera Securities
Bright Trading
Hold Brothers
Of course, as always, do you own research/due diligence, and look at the SEC.gov focus reports and FINRA brokercheck before joining any prop firm.