Is it okay to feng shui the attic without a suspended ceiling?

No such thing!

As long as the Feng Shui of the house itself is good, it is enough. There are many buildings with beams, and there are many houses without suspended ceilings. Even if there are any problems, they are caused by others. It's not affected by this.

As long as there are no problems with the surrounding environment, floor, apartment type, interior layout, furniture arrangement, etc., everything will be fine. Don’t worry about beam problems!