If "The IMAX Experience" doesn't appear on the cover, then yes it belongs in the Original Title field.

I've always seen "IMAX" shown in full capitals (IMAX Corporation). A Google search seems to show that's almost always the case.

It seems like the correct Title according to the front cover would either be "IMAX: Nascar" or "Nascar: IMAX". Does it show how the title appears on the spine or a back cover credit block?

Then again, NASCAR (National Association for Stock Car Auto Racing) is often shown in full capitals also...

Quoting CubbyUps:

Quote:
The Spine is the same as the front cover.

The back cover's credit  block has "NASCAR: THE IMAX EXPERIENCE".

So it looks like it would be:
Title "IMAX: NASCAR
Original Title "NASCAR; The IMAX Experience"

Correct?

Yep, that sounds correct to me.

I don't want to muddy the water, but could IMAX be considered an edition?
Have other IMAX DVDs been released with a similar title setup?

Except bunch of different studios release IMAX titles and they title them slightly differently.  IMAX is a movie format, not a series format.  For my personal sort title, I title all of them IMAX: Title name, but that doesn't work for lot of them. For example

The Living Sea
Coral Reef Adventure

have a header "Originally Created for Exhibition in IMAX Theatres" but does not have IMAX in their titles.

There appear to be 229 profiles in the database that have IMAX: "Title here"

I kind of doubt it's the edition...