I use phpBB2 right now if I switch to phpBB3 or invision style will my forum look (CSS style) change as well?
Yes it will.
Is there any way to preview my forum in those other types without actually changing it full over?
Generally its better not to change versions from the admin panel. It will mess up the looks of your forum. Just go onto hitskin.com & choose whichever skin you like for those specific versions.
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