Confusion regarding car registration

Hi, I'm moving down from the East Coast this week and know that I have to get my car registered in TX within 30 days of moving here. The vehicle inspection shouldn't be a problem, but I've been looking at availability at the tax office (https://www.hctax.net/Auto/Appointments/Appointment) but I work on weekdays so probably won't be able to go then (I do see appointments starting 7:20am which would be ok, but online says the offices open at 8??)… I've seen online that occasionally walk-ins are accepted, does anyone have experience with getting a walk-in in the past month or so? Or using a third party like https://www.thetexasautotitlecompany.com/ or any other potential solution like if it'd at all be possible for me to do this online/through email/phone/mail? I'm just out of college and this is my first time doing all of this… would appreciate any help. Thank you!