Care to post which mods you are using?
Certainly, I will even explain why I'm using each one:
Better Trophies
This is pretty minor, but I found the original trophies utterly trivial and with almost zero impact in terms of gameplay. This mod makes them somewhat useful, without breaking balance. It's not for the power, but for the sake of the feature having a reason to exist.
Endure
This mod enables "durability" customization for all items. First of all, I hate durability in most games - and it's particularly poorly done in Witcher 3. Not only does low durability have a pretty neglible effect - making the concept utterly useless, but items also "break down" extremely quickly. While I can easily live with 10% reduction in performance - it's annoying and the "red marker" on the UI is a pain in the ass (I know I can disable it). So, I use this mod to make Relics and Witcher gear indestructible - to save time and frustration - again without any kind of real balance impact, because the performance impact of a nearly destroyed item is very low - and they never actually break.
EnhancementSystem
This is one of the more important mods. It makes non-Witcher items - and specifically Relics useful when compared to Witcher sets. It means there's a decent chance of finding the occasional upgrade when you loot stuff. Mostly, we're talking small upgrades - but counter to my experience with the non-modded game, Witcher gear isn't as dominant with this mod - and it makes exploration a lot more enjoyable for me. Also, even more importantly, it makes the various Relics stand out in terms of their bonuses. It means you're likely to use them for specific fights - even if your Witcher gear is "more powerful" in terms of pure DPS.
Fast Travel from Anywhere
This is pure convenience. It's minor because fast travel is already very lenient - and the primary reason I use it is that I can fast travel when I'm on a horse. Without it, I have to actually get off my horse and touch a travel post, travel, and then get on again - which is annoying and stupid.
HD Reworked Project
The defacto texture mod, I guess. I don't really think the game needs it - but it's definitely an improvement so far as I've seen. I could take it or leave it - but why not have it when it's there.
No Story Intro
Just makes the game load faster. The story intro also requires you to manually skip it - and the game doesn't really tell you when it's done loading - which is another stupid thing.
9000 weight limit mod
Gothic/Risen spoiled me, I admit it. I absolutely despise the excessive inventory management in games with hordes of loot - and, boy, does Witcher 3 ever have a TON of completely trivial loot. The default weight limit is almost sadistic, if you ask me. For SOME games, I think it makes sense to have a weight/inventory limit. Games that go for that total immersion can make it work. But in vanilla Witcher 3 - you can still carry enough weapons to make any army proud - which sort of defeats the whole "realism" angle. In that case, I always pick convenience - as there's no power advantage of any kind involved.
Set XP multiplier
I consider one of the primary design flaws of Witcher 3 to be the fact that you earn almost zero XP from the vast majority of battles you fight. Since a HUGE amount of the game is fighting - I think it's an utterly terrible idea to not reward the player, especially when the fights are tough. So, after a lot of testing - I've found a 3 x multiplier for kills is a good fit. To compensate, I've reduced quest XP to about half. Since you still gain the majority of XP from quests - it's sort of the same overall, it just feels a LOT more rewarding when you go freeform exploring or you have to kill the endless respawning enemies over and over again.
Slots, slots slots
This is another major one. In vanilla Witcher 3 - I found the available skills slots too limiting. You simply couldn't comfortably create an interesting build - and you had to use a ton of slots for relatively boring upgrades, because of the mutation system. I use the "balanced" version - which means you don't actually get more slots until you're very high level (34+ for the first one) - which means it doesn't affect your power that much, because you're already extremely powerful at that stage. But it means you can experiment a little more - and mix and match certain physical skills with the signs. The reason it's important to me, is that I hate feeling like I've "finished" my character before the game has ended. I tend to lose interest when I can no longer make meaningful progression - so I kinda need something for the higher levels, as I expect the game + DLC will take a very long time to complete.