Good job! You almost got everything right!
Sorcerer Tower
Top Path has as much damage as Bottom Path as showed below, though the Top Path has an AoE. That's why Top Path is way better.
Artillery Tower
Depends, at the start of the game, to defend the first waves of troops, Bottom Path is the superior one with more DPS. In Skeleton IV+ defence however, the synergy between the Sorcerer and Artillery Top Path results in more damage than when using Bottom Path. Also, Skeletons are immune to Bottom Path starting at Level II.
Although this is all true, (if you got enough Coins for it) I suggest you only use Sorcerer (of course combined with Ice and Quake) for Skeleton defence. This will keep the front row empty for Archer Bottom Path Level IV later in the game. If you have enough Coins, you could immediately place some Archers to assist the Sorcerers.
Poison Tower
Top Path is always placed at the start of the track, no matter what. But in case your opponents send Slimes the Poison effect disappears when Slimes split. That's why some Poison Bottom Path are useful from halfway down the track. They have a higher DPS than Top Path.
If you are interested in more defence strategies, then they can be found here:
https://www.cubecraft.net/threads/td-full-guide-strategy.271970/