Does this only affect NPCs or does the player have more reach aswell?

Yes, the player's reach is increased too. The mod affects the weapon and thus everyone who wields it.

Do I need to install Unofficial Oblivion Remastered Patch for this mod to work?

No, you don't. The "UORP" at the file name means that the changes from the Patch was merged into that .esp, but UORP is not a required master file for those .esps and there will be no issues with the game. Au contraire, only benefits.

Do I need to install Balanced Unleveled Rewards for BUR versions to work?

Nope, they're standalone. Though that would be weird to play with only two-handed weapons unlevelled =) But technically, you can do this.

I have the Deluxe DLC. Do I need both Main and Deluxe files?

Yes, you need both.

There are so many files in the archive. Which one do I need to install?

You choose only one. Please, refer to the list of versions in the mod Description or in the archive's Instructions.txt.

You say that this mod increases the reach, but it says 0.95 reach almost everywhere. What does it mean?

That's 0.95 of 2006 Oblivion Reach. In the remaster, Reach values for weapons were reduced, and for two-handed weapons they went way too low. For example, 1.3 reach was changed in Remastered to 1.1 - that's 84.6% of the original value! And I am, not being sure that reverting it back to 1.3 would be a good idea, changed it to 95% of the original. For example, if the original reach is 1.3, then with this mod it becomes 1.235. That's not a drastic change, but that's enough to at least reduce the player's frustration and fix NPCs' behavior.

What is the recommended load order?

Something like this:
Unofficial Oblivion Remastered Patch.esp
Unofficial Oblivion Remastered Patch - Deluxe.esp
TwoHandedRangeDmg_UORP_x2.esp
TwoHandedRangeDmg_Deluxe_x2.esp

Breakdown:
Main file must be loaded after all Oblivion DLCs, UORP, BUR, whatever else you have that changes weapons behavior.
Deluxe extension must be loaded after all Oblivion DLCs, UORP Deluxe, whatever else you have that changes Deluxe weapons behavior.
Main and Deluxe files include different weapons, thus they do not collide with each other and may be loaded in any order.

Is it possible to adjust the speed of the two handed weapon as well?

Nope, it's an animation bug for claymore and warhammer animations. We need an UE pak fix for that.

Is this mod compatible with damage slider mods?

It is compatible with damage slider mods (like Difficulty Slider Fixed) since they only change Game Settings values. Tho if some of them change weapon stats as well, those will be ignored/overridden.

Is this mod compatible with the Ascension?

Yep. Mostly. To be precise, there are only minor differences in stats for 4 unique weapons. Just remember to put this mod after the Ascension.

And the Descension?

Totally compatible.

And the Auto Upgrade Leveled Items?

Totally compatible.

Do I need Depletion Weapon Fix with this mod?
If you don't have the UORP, then you'd probably like to install that fix. But keep my mod on top of that — they override each other, and all versions of this mod already include all the fixes necessary.

Can you make a version with compatibility to Inventory Sorting Tags?

Probably, but not this week. In fact, I'd rather wait for a more versatile OBSE64 script that would autolabel items based on their type.

Any chance we can get a version for Game Settings Loader?

There are no related settings except for global damage mult. So no, it's not possible to achieve the same result with Game Settings only.