I tested the beta and it did not change anything for me. I can also confirm that Webstart runs 32 bit and normal as 64bit per "about" dialogue.

I tried to fore 64bit for webstart with the command below, but when I checked the about it still showed 32 bit and it was still fast

"C:\Program Files (x86)\Java\jre1.8.0_144\bin\javaws.exe" -J-d64 http://www.sweethome3d.com/SweetHome3D.jnlp

The easiest way to tell if it is slow or fast is when I load a file and all the furniture just has the clock symbol on it, then I know it is slow even without trying the 3D view. It then takes maybe 5 seconds for each piece of furniture to go to it's rendered color in the plan view.

Luckily webstart still runs fine.