County sheriffs aren't typically responsible for traffic enforcement in Texas; that's the job of the local police department within city limits, or the Department of Public Safety (DPS) between cities. DPS officers are typically called troopers. They wear hats with a flat brim, unlike sheriffs, who typically wear cowboy-style hats. Each county only has one sheriff, and they usually work in an office. It's unlikely a sheriff's deputy would ever stop you, unless they had some particular reason to suspect you of something like drug trafficking or another crime. The same is true of the Texas Rangers, who are a statewide agency.
There is nothing very new about traffic enforcement in Texas that I know of, except for roadblocks within about 100 miles of the southern border. If you visit far south Texas, you could indeed be stopped, unless you look obviously non-Hispanic, or they have a license-plate reader that marks your car as a rental or something. That's just hearsay, I haven't been there myself.
I can't vouch for the knowledge or patience of all Texas law enforcement personnel, so, as when driving anywhere, you should be prepared to be polite and cooperative if they ever stop you. (Don't get out of the car, just pull over, open your window, keep both hands in sight, and get out your license, ID, and proof of insurance.) But as far as I know, it shouldn't be a problem as long as you also carry with you your passport as a photo ID.
According to the DPS website,http://www.dps.texas.gov/DriverLicense/recipr...
German drivers between the ages of 18 and 75 are allowed to use their valid German license for up to one year, under the terms of Article IV of the NATO agreement. It doesn't say anything about the license having to have a photo on it as far as I can tell. (No idea what tourists over 75 are supposed to do; that one was new to me.)
The DPS site does mention that foreign driver's licenses are supposed to be translated into English. (!) While I very much doubt that every foreign tourist who rents a car actually does that, I suppose you could have it done if you had time and wanted to avoid any possible hassle.
Texas also has the requirement that all drivers must carry written proof of insurance, so you should check with your auto insurance company or your rental car company about that.
The DPS site is full of obscure stuff and not very easy to navigate,https://www.dps.texas.gov/siteindex.htm
so I searched out the driver handbook for you, which you might want to skim through if you're planning on doing a lot of driving, or if you have trouble sleeping on overseas flights. (-;http://www.dps.texas.gov/internetforms/Forms/...
Again ohne Gewähr, but from memory, a few key points:
• all passengers must wear seatbelts
• babies and small children must be in car seats in the back seat
• passing in a marked lane on the right is legal; nevertheless, slower drivers should keep right
• right turn on red after a full stop is legal (also left turn on red from a one-way street to a one-way street)
• if a police or emergency vehicle is stopped with lights flashing, you must either move to a lane farther left to avoid it, or reduce your speed to 20 mph under the posted speed limit (p. 49)
• traffic penalties are higher for violations in construction zones ('work zones') when work is in progress, or school zones when yellow lights are flashing
• maximum blood alcohol level is .08%
• open containers of alcohol are not permitted inside the car
• the legal drinking age is 21 (!)
• marijuana is not legal
• texting or using a cell phone while driving is generally legal except in school zones, though some cities may have more specific laws that require hands-free cell phone use
• many cities formerly had red-light cameras, but the state legislature has just made them illegal
• speed limit where unmarked is typically 30 mph in a town or city, 70 mph in the country; certain sections of highways in West Texas, or toll roads, may have higher marked speed limits
Texas doesn't generally have speed cameras, but it does have radar enforcement via both marked and unmarked cars and motorcycles, and occasionally via airplane or drone in sparsely populated areas. Most large-city police departments are too busy to stop many speeders, and in most places you can typically drive 5 to 8 mph over the speed limit without worrying about being stopped, but certain small towns may be known as speed traps.
If you're planning to do a lot of driving, especially in a large city, you might want to try a phone app such as Waze, which can be handy to warn about delays caused by construction or wrecks. (Though it's owned by G**gle, so don't leave it turned on or let it access your data unnecessarily.)
For country roads, which are usually more scenic and less stressful, I still prefer a printed map, so you can compare the choices of route more easily. AAA provides maps and guidebooks free to members on request; you might phone your local ADAC and see if they would just mail you some, if you're a member.