need clarification of china 24hr transit visa

Mushfiq, it is important to use correct terminology because this is not 24hr transit visa, but 24 hour visa free transit, so there is no any visa involved.

Both of your itineraries are eligible for 24 hour visa free transit because your total transit time will be less than 24 hours long. You should know that the transit time is counted from your scheduled arrival until your scheduled departure. Also, it is fine to travel on separate tickets and unrelated airlines as long as your itinerary is within the rules set for 24 hour visa free transit.

When you travel on 24 hour visa free transit, your right is to travel visa free and to stay in the transit area of the airport. There is a possibility to apply for a temporary entry permit if your layover is a long one and especially if it happens during the night. Essentially, obtaining a temporary permit is not a passenger's right, but more like a bonus offered to those with long layovers, but even then based on discretionary decision of the immigration official on the day of your arrival.

In other words, you would be better to choose your first option if that means traveling on separate tickets. If that is the case, that the Chinese immigration authorities will definitely grant you a temporary entry permit because you will have to collect your luggage and perform new check-in and that is possible only if you literally enter China. So, if you choose the first option, the first thing that you will do upon landing in Guangzhou will be to approach 24/144 hour visa free transit counter where you will apply for a temporary entry permit by presenting your flight tickets and your hotel booking if you plan to stay in the hotel overnight. When the permit is granted you will head to the immigration and then spend some time in the area on your own. Have a nice journey.