1. Post-Only GTX
It is a function that prevents the trade at the market price when trading at the limit price. If you trade at the limit price, the price that is contracted the market price will be automatically cancelled.
The reason for using this feature is to make sure that when you try to buy at the limit price, it doesn't get bought when the price is suddenly lower or higher than expected and the standard point of 'long' is lowered. Also, if you check 'Post-Only GTX', you can use it if you do not want to pay the market price(taker) fee because the order is automatically canceled when the market price(taker) fee is paid.
2. Reduce Only
Reduce-Only is a function that reduces the amount in the position you are.
This is to prevent the possibility of a larger amount due to your click miss.
For example, if you are in a Long position, you can no longer buy and only sell.
If you are in a Short position, you can no longer sell and only buy.