I've been asked to put a new vinyl tile floor over an existing vinyl floor.
If the old floor is in good shape, I'm considering using a floor leveler
product first then thinset mortar before using the peel and stick tiles.
Option 2 to install 1/4 lunan with ringnails then applying thinset before
installing the tiles.

My question is the thinset overkill ?
Any other suggestion ?

Thanks
Dick

use armstrong commercial tile instead since you're doing it right the
first time and follow installation instructions in the box similar to
your option 2, including a separate can of specified adhesive.
the self stick tiles have a shorter life.
see:
http://www.armstrong.com/home/us/en/

Yeah, do it the right way and remove the old tiles first.

Assuming the old floor is in good shape, you can put the new tiles
right on top. Just clean up the old floor so the adhesive will stick,
and fix any bumps or lumps in the old floor.

As for overkill, if you were going to level the floor etc, you might as
well take out the old floor - which could be a pain.......

Regular old self stick tiles should work fine and last a long time;

I think leveling the floor is probably overkill for this job