This is not first hand information, but from what I can gather. The Silent Topre borders don't have a different feel or stroke. The only thing effected is the sound reduction when the keys snap back after release from a key press.
The Realforce has a different sound than the HHKB due to construction, size, build, etc. For example, Realforce slider housing mounted on a plate, while the HHKB's slide housing is part of the keyboard's plastic frame. This will result in a different sound.
The key feel for the HHKB compared to the Realforce is the same, or at least I can't tell the difference comparing it to my friends HHKB.