I'm happily running a mix of Ursine/Wolven/Assassin armours (Gauntlets are Assassin for the +10% crit). Ursine Swords and Bow, unless I *really* want additional sign strength when I can swap out for Griffon.
I also have the Griffin and Feline sets and will swap out pieces as needed when making a foray into "elemental" territory, or going "monster hunting" to get the highest resistance for the threat I think will be the strongest. Armour value is of minor importance if it is close, and resistance is *much* more significant. Early in the game I ran Griffin or Nilfgaardian or Undvik armours depending on whether I was heading to human or monster infested areas. I wouldn't swap out for an individual minor encounter, but would prior to a contract battle, or when entering/leaving the more infested regions. (E.g. spitfire bluff for humans, prior to taking on Witchunters etc... Crookback bog for monsters etc). Complete "sets" of the Witcher armours are often completely ineffective at resisting one or more attack types, as are most 'ordinary' armour sets (they usually cannot resist elementa or monster attacks). There are a few specialist armour pieces that are *ideal* for tackling venomous or fire using monsters, with 100% resistances ~ I don't actually carry or use these but they could be useful to seek out if these enemy types are troublesome.
I've always liked my fast attack build with alchemy, though I had some signs earlier when there were fewer rune and glyph slots for the *basic* Quen and Axii strength needed to be modestly useful.
My current Alchemy skills equipped are Poisoned blades, Protective coating and Frenzy. Combat skills are Muscle Memory, Precise Blows, Whirl, Crippling Strikes, Fleet Footed, Deadly Precision, Resolve, Undying, Razor Focus.