Don't have much to say about the rest of the comment but
>The spread on most trades is probably in the range of 50c on low liquidity shares and $1 on low liquidity options.
Is demonstrably wrong. The minimum spread on options contracts is $1 and the spread on liquid options contract (not SPY liquid but like TSLA or AAPL) is generally in the mid $10s and often hits $100+ on ATM contracts). Right now an ATM call on AAPL a month out quotes 4.75 to 4.85 which is $10 and the same on TSLA quotes 44.05 to 44.40 which is $35. Not a trivial amount, and it implies that the broker could get price improvement that is an order of magnitude more than the typical commission on options (~1$ per contract).
RH sets an initial default value for the limit order at the middle point between the bid/ask. You are in control of your limit order pricing there. If you wish to join the queue at the bid you can. There is no option for a market order. You can leave your bid and wait to be filled same as others.
>The spread on most trades is probably in the range of 50c on low liquidity shares and $1 on low liquidity options.
Is demonstrably wrong. The minimum spread on options contracts is $1 and the spread on liquid options contract (not SPY liquid but like TSLA or AAPL) is generally in the mid $10s and often hits $100+ on ATM contracts). Right now an ATM call on AAPL a month out quotes 4.75 to 4.85 which is $10 and the same on TSLA quotes 44.05 to 44.40 which is $35. Not a trivial amount, and it implies that the broker could get price improvement that is an order of magnitude more than the typical commission on options (~1$ per contract).