10 Abjuration Wizard/1 White Draconic Sorcerer/1 Tempest Cleric (build for Int/Con rather than Cha/Dex) is a good alternate for your CryoCannon. It just trades the Draconic damage rider for being unkillable by lvl 4.
Your Speedrunner build might want to trade 1 lvl of Gloomstalker for 1 lvl of Champion Fighter. Extra Crit range is quite a bit better than Natural Explorer/Favored Enemy.
The Flashbang is missing it’s major components: Luminous Armor and Callous Glow Ring, that turn it into a true AoE debuff shutdown build.
For other builds, some of my personal favorites are Eldritch Knight 11/War Cleric 1 built for Tavern Brawler (Lae’zel), Paladin 2/Swords Bard 10 (Minty), Thief 4/Swords Bard 6/Fighter 2 built for Sharpshooter (Astarion), Wildheart Barbarian 8/Thief 4 built Bear/Stallion (unkillable) or Tiger/Tiger (insane damage) with GWM (Karlach), Conjuration Wizard 11/Storm Sorc 1 as a control build(Gale), Necromancy Wizard 6/Life 4/Spore 2 unkillable nearly infinite necrotic damage (Gale), Hunter 11/War Cleric 1 built for Punch Drunk Bastard for insane AoE damage (Minsc).