the GOG build is using DX9 (the NewDark engine update), so it will run in any modern resolution - even eyefinity 5 is not a big problem.

Thief™ Gold and Thief™ 2: The Metal Age

Changelog for update Patch 1.24 ND (GOG-54 and GOG-25, respectively) (added 04 April 2016):

This is a hotfix for v1.23 that fixes a couple of things.
- In particular the broken "sun_runtime_obj_shadows" has been fixed. In DromEd the crashes related to DXT
- textures have also been fixed (if "dxt_to_rgb32" was enabled as a workaround for those crashes then it can be removed again).

General:

- fixed broken "sun_runtime_obj_shadows" (worked in DromEd but not the game exe)
- fixed path priority order bug with subtitle files (was accidentally reversed)
- reduced risk of the door drifting bug that can happen in some occasional FMs (door-based objects that should rotate but instead of rotating just float away into infinity)
- added "no_unload_fmsel" option to cam_mod.ini (can be useful if experiencing crash with FMSel, especially on Win10)

DromEd:

- fixed DXT related crash (when running editor in HW mode)
- fixed crash accidentally re-introduced in the previous version when loading (old) missions with bad door objects (objects internally flagged as doors despite not being doors)
- fixed ambient sounds disappearing after playing in-game movie
- fixed link data for certain link types (AIWatchObj) getting reset when reordering them (in link list dialog)
- fixed original glitch in vhot evaluation that could under some circumstances affect "show_vhots", coronas and particle attachment links using vhots
- fixed DML syntax error bug when working with links that have no data set
- fixed missing field indexing in DML export (for properties that contain multiple fields with the same name)
- fixed a bug that could occur under certain circumstances with StimSource and Receptron commands in DMLs
- fixed a few crashes that could happen in rare situations
- fixed buggy transform for vhot and subobj detail attachment links when parent object is scaled
- added mono warning for ObjTxtReplace properties with textures that couldn't be found/loaded
- added "spew_stimulations" command to toggle mono output for stim events

This latest update for Thief Gold introduces a bunch of stuff that makes me wonder whether it‘s there on purpose or by accident. As I understand it, Thief Gold is sort of reverse-engineered on top of the NewDark Thief 2 files, so some gameplay elements distinctive to Thief 2 have made their way into the original Thief (one example would be guards making a run for it once you‘re taking aim at them when out of their reach). But the latest update includes lots of really distracting modifications that I can‘t help but think they were mods/bugs that were left in by accident.

Here are some of the worst offenders (and this is just from a quick playthrough of the first couple of missions):

- the very distinctive angry-looking Bafford guards have been changed to much friendlier looking fan-made Hi-Poly models
- some of the in-game items have been changed to fan-made models (the cameras in Cragscleft Prison)
- shooting said cameras no longer makes a loud clanky noise and doesn't alert the nearby guards any more
- The lighting seems completely off in some places. Namely the entrance room inside the Overlord‘s Fancy, which in all previously released versions included some strategically-placed shadows, is now lit up like a Christmas tree
- check out the two Hammerites having a conversation when leaving the mines: knocking out the one who has his back turned to him used to cause the other one to go into alert status, but not in the latest version

The previous version had none of those problems. The only difference I found compared to the unmodded original as far as in-game items/models were concerned was that the blue keys were changed to higher-poly gold keys. That wasn‘t too big a deal, but there‘s something SERIOUSLY off with this new version. I never used the rollback feature for Galaxy, but in this case I‘m more than happy it exists...

the default GOG build includes none of those changes/enhancements - you must have (accidentally?) installed TFix.

I did install the German Language Pack, so maybe that's the cause of the problem.

Anyway, I just installed the game via Galaxy on a different machine and I still get the same bugs/modded models.

ok, then we might have a problem, as that probably means GOG has patched their build with TFix instead of using the GOG package. I'll check the Galaxy build, and if that's the case, GOG will be notified (as bundling full TFix is a bad idea for several reasons).

and just for your info, those are not bugs, but deliberate choices (maybe with an exception of that hammerite, I might have a look at that later), and I had good reason for doing them. hardcore purists hate them, but it's impossible to please you guys by definition, so I usually don't care too much - TFix is meant for the average Joe Taffer.

looks like GOG included elements of TFix, but are rolling it back today.

You need to organize your thief builds.

Maybe get a new leader for your thiev guild? There is a few in Ankh-Morpork

Thief™ Gold and Thief™ 2: The Metal Age

Changelog for patch 1.25 ND / (Windows) (added 03 April 2017):

- fixed position on a few really badly placed objects
- it's now not possible to bug out impassable (decorative) doors in the Training and Assassins missions
- alarmlights in Cragscleft, Assassins and Undercover now work properly (red light when triggered)
- Constantine was not using all of his attacks in the last level because of incorrect link settings, this is now fixed