For funsies, these are the suggestions/feedback I gave to Flamestrike on Encounters 1 & 2:
Some snowy terrain in this scene can aid the wolves, especially if the PCs enter somewhere between the room where the giants are such that if the PCs hear the giants, they might not notice the wolves hidden behind them before it's too late. And since the spellcasters are likely to be in the back ranks of the marching order, this synergizes with Gorbarth's tactic of having the wolves take down obvious spellcasters. The snowy terrain might be considered a situational advantage for the enemies, however, which would increase difficulty by one step. I personally wouldn't consider it a big enough deal to rise to that level, but others might. If it is seen as a situational advantage that steps up difficulty, then you may as well go all in and have it be magical snow that empowers cold magic and other effects. When the winter wolves are standing in the snow, their breath weapons are more powerful, imparting disadvantage to the targets' saves.
You mention a pit being removed, but I would consider keeping it in there and making it about 30+ feet deep. Then I would change Gorbarth's axe to one where it either shoves on a successful hit or gives him advantage on ability checks related to shoving. Maybe make it an oversize maul or greatclub and call it Bully's Bludgeon or something like that. Knock the melee guys into the pit so they lose a turn or more getting out. Maybe put the scroll of telekinesis down there as a booby prize. Since the pit can be used by either side, it doesn't increase difficulty. The giants' height might make it easier for them to climb out, however.
For the social interaction component, I would consider making any end to hostilities be contingent upon the PCs and the giants taking a blood oath not to mess with each other. This ritual act costs each PC a hit die, but guarantees the frost giants will not double cross them lest they draw the ire of their gods. It both fits the theme of the frost giants and drains some resources.
The battle with the death slaads seems interesting. The heavily obscured nature of the place will hamper the ranged characters, but I imagine they'll have races with darkvision for ranged PCs. I would suggest that the slaads are at the top of a steep incline that poses a difficulty traversing (perhaps it's covered in horrible slime). A rusted lever somewhere in the starting area creates steps on the incline which avoids the slippery climb, but it requires great strength or some skill with tools to make it work. The incline might be seen as a situational advantage for the enemy, but the guidelines say if the PC also have an advantage, they cancel each other out. So I would suggest providing a couple areas of rubble which provide cover down where they enter.
This setup will synergize with cloudkill which flows downhill, plus that spell's heavy obscured condition means the ranged guys are shooting blind. Few characters are also proficient in Con saves. Fireballs follow. I would suggest having one slaad visible, but shapechanged into a "helpless" little girl who is scared of some lurking monster and has valuable information to share about the metal man elsewhere in the dungeon if only she weren't so scared. This sets up some potential social interaction. I might even put her down where the PCs come in while the invisible slaad lurks up the incline behind the statue and offer characters the opportunity to take disadvantage on their own save in order to protect the little girl from cloudkill/fireball damage. How delicious it will be when the players are sacrificing resources to save her only to see her shapechange into a slaad and tear into their back ranks!