Yeah, no surprise that you are having problems. Most of the time players can manage about 3 to 5 mods before conflicts occur. If you are very persistent and careful then you might manage 8 to 10 smaller mods. There just isn't any way that the game can possibly work with all 16 of these mods. The mod system mainly works by making text edits to the game's code by applying changes found in mod files. When two mods change the same code we call it a conflict or overlapping changes, which usually result in bugs, errors, or crashes.
The error messages consist of multiple parse errors, which happens when multiple mods change the same code thus mutilating it beyond comprehension. After a parse error, the engine fails to load the entire file, thus your game has no code to run person descriptions nor quest-line events. In debug mode, the game will fail out of the code to report a problem as soon as it tries to use these non-existent files. In normal mode, the game will tend to ignore the non-existent files until a fatal problem occurs. Some of the game's files don't load until a progress is started, so the problems in those files have not been processed yet.
Constants, randomportraits, and Quick Defeat Animation are probably the exceptions to conflicts as they mod very unique places in the game that almost never change and have very small code profiles. They are very unlikely to conflict with any other mods when applied last in the list, though they can still be harmlessly erased by mods replacing specific parts of the code.
AricsExpansion is probably the largest mod to ever be created and touches nearly every part of the game. It requires the Bugfix mod and is known to be compatible with Constants and randomportraits. It fatally conflicts with both Es-01, Es-02, MoreGenderOpions, ProtagMod, and Drake's Descriptions. It is probably conflicts with most other mods.
The Bugfix mod is probably the second largest mod on the list and touches many parts of the game though it tends not to significantly change the game mechanics. It will still conflict with any mod that attempts to mod the same code, such as the Chastity Belt mod and the ProtagMod.
The Expanded Sex mods, Es-01 and Es-02, are fairly large mods that are mostly focused on interactions. However, the current version of the Bugfix mod cleans up a lot of code related to interactions so there are some minor conflicts.
MoreGenderOpions is a relatively small mod, however it changes some rather common files. It fatally conflicts with AricsExpansion, As long as it comes after the Bugfix mod it only has harmless(some quest text will display wrong) conflicts. Changing the gender assignment can behave weirdly on characters with a chastity belt from the Es-02 mod.
The ProtagMod has leading spaces instead of tabs in spells.gd so the Domination spell will not work unless that is fixed before applying. It also harmlessly conflicts with the Bugfix mod.
Many of these mods appear to be Drake's mods, which are rather new so I'm not entirely familiar with them. They appear to be quite small thus unlikely to conflict with most mods. I don't know of any conflicts with the following: Alchemy For Dummies(will not change potions added by other mods), Perfect Trait, and Line 126. Gender Equality appears incomplete and mostly mods an unused file and though it can result in some odd descriptions it does not appear to conflict with anything; however, the increased breast size on males can result in them changing into Dickgirls with AricsExpansion.
Drake's Descriptions appears to only conflict with AricsExpansion, which will bypass most of the changes and cause a parse error for one.
Beauty Adjustment appears to only conflict with AricsExpansion, which will bypass some of the changes and erase the rest if AricsExpansion is lower in the list.
No I in Race would conflict with AricsExpansion, but some typos mean that this mod does nothing.
Combat Stress Reduction conflicts with AricsExpansion and will likely result in parse errors.
Hopefully that covers most conflicts, there are a lot of combinations to check for so I may have missed some.