It is a misconception that open carry of handguns is generally prohibited.
The Penal code makes the carry of handguns, on or about your peson, illegal. No mention is made of concealed or not, loaded or not.
Section 46.15 of the penal code states when it is NOT illegal to carry a handgun. The only clauses in that section that requires the handgun to be concealed to be legal is for a person carrying under the authority of a CHL, or as a Personal Protection Officer.
That section also requires armed guards to carry "in plain view" and all of the other sections allowing the carry of handguns are silent on open or concealed, meaning you can carry however you like.
So the following can carry however they like;
A person who is in the actual discharge of official duties as a
member of the armed forces or state military forces as, or as an employee of a penal institution who is performing a security function; or as a guard employed by a penal
institution;
A person who is on the person's own premises or premises under
the person's control
A person who is traveling;
A person who is engaging in lawful hunting, fishing, or other
sporting activity on the immediate premises where the activity is
conducted, or is en route between the premises and the actor's
residence, if the weapon is a type commonly used in the activity;
A person who holds an alcoholic beverage permit or license or
is an employee of a holder of an alcoholic beverage permit or
license if the person is supervising the operation of the permitted
or licensed premises.
As far as the TABC guys;
Texas Penal Code
§ 46.02. UNLAWFUL CARRYING WEAPONS. (a) A person commits
an offense if he intentionally, knowingly, or recklessly carries on
or about his person a handgun, illegal knife, or club.
§ 46.15. NONAPPLICABILITY. (a) Sections 46.02 and 46.03
do not apply to:
(1) peace officers or special investigators under
Article 2.122, Code of Criminal Procedure, and neither section
prohibits a peace officer or special investigator from carrying a
weapon in this state, including in an establishment in this state
serving the public, regardless of whether the peace officer or
special investigator is engaged in the actual discharge of the
officer's or investigator's duties while carrying the weapon.
Texas Code of Criminal Procedure
Art. 2.12. WHO ARE PEACE OFFICERS. The following are peace
officers:
(6) law enforcement agents of the Texas Alcoholic Beverage
Commission;