For enemy scaling I use
Dynamic Enemy Scaling - Enhanced which you can fully customize to your own liking and the mod author suggest other neat mods on the description page to be used with it.
To make the combat less frustrating the
No Auto Sword Sheathe - Unsheathe mod is of course a must so you yourself can fully decide when to pull out/sheathe your sword and which one to use.
To get rid of HUD clutter I mainly use
Friendly HUD (which also does many other things than just changing the HUD) and
Unseen monsters in order to not have the game point out to me exactly where a monster is when using the witcher senses.
For alchemy I use
Witcher 2 Potion Length, does what it says really but also lower effectiveness so while that swallow potion might last longer it will also take longer to heal you. I found it too easy to refill all my potions though however by abusing the meditation system so I used the configuration file that came with Friendly HUD and set it to only allow meditation near fire places. To not screw myself over completely though I also installed
Sit on demand which enables mediation with a different button and I set that one to create a bonfire so I can still meditate on the open field (provided I have timber on me as creating a bonfire costs timber).
Some other neat mods.
The prevent all file from
Apply Oil Bug Fix, prevents me from during inventory management during combat, forcing me to prepare (like a Witcher should).
Remove Weapon and Armor Level Restrictions, does exactly what it says. If I found it or crafted it I earned it.
Fix Exp for quest, grey quest will now give XP.
The Human behaviour file from
Brutal and Realistic Combat, makes human opponents smarter. For example they will now counter you if you spam attack them while they're blocking.