PathOfExile.exe vs. PathOfExile_x64.exe

Maybe it's related:

When I installed the game on Win7 (x64), the installer put the non-64b exe into the desktop icon. I played a bit with it, but it had much lag (even though ping was <40ms) and often disconnected. Then I discovered the x64 exe file, ran that, and since then I had no disconnection and only rare lags. Not sure if really the change of exe file was the solution, but seems so.

update:
after some more days of playing both versions, now I don't see the same difference as on the first day. Both work well at some times and lag or disconnect often at others.
(I think it's worse than when I played it years ago on win xp...)

When I launch the game via the PathOfExileSteam exe instead of PathOfExile_x64Steam my task manager has the PathOfExile_x64Steam listed as running app.
Would like to play in 32bit mode since my PC is weak and I dont want shadows in game.
So how to run the 32bit version of the game?