3LCD projectors do not have sealed light paths. DILA/LCOS and DLP use sealed light path(s). Now, I have read one person say that just because it's sealed does not absolutely guarantee that it cannot get a dust blob. That said, I have never once read of a JVC owner with a dust blob, but there are probably hundreds of LCD projector owners complaining about dust blobs on various forums. All of the 3LCD brands will get hit.
You can't necessarily use propellant air, as the stuff in that mixture, the pressure, and the very different temperature, can actually cause harm to certain parts, and that it may not be enough to clean it anyways, besides just moving dust all around to other inaccessible parts.
OTOH, there are for certain models, consumer written instructions for cleaning dust blobs. I think I just posted one recently for Panasonics, lemme search my posts . . . .
Ok, here are instructions for cleaning the Pana 3000. I found one set for the 2000, but they seem skecthy to me TBH, and haven't run across one for the 4000 yet.
Successful Removal of Dust Blob
Are the JVCs very flexible with placements (horizontal/vertical shifts)?
Yes, like LCD PJs, they are quite flexible. A different world altogether from the vast majority of DLP projectors.