Rollerskis are fun, too. Despite of what you think snow skis
are much harder to balance properly than rollerskis. Snow is very
forgiving and when your ski is not "flat" you'll slow down but still slide.
On rollerskis you HAVE to keep balance and that is easier to learn.

Very good that you are getting confused - you should!
Rollerski market is an interesting one. There is so much crap, it
is mind boggling. Stay away from anything less than 100mm wheel.
Stay away from pneumatic wheels - don't get me wrong - concept
is good, but there are flats, worn (and expensive) wheels and such.

Stay away from racing rollerskis - they are too fast and, in my
opinion, just a little too short.

A lot of how rollerski feels is in the wheels, the beam itself is
not that important, but I would choose aluminum for lightness, durability
and price.

4-wheel (80mm) rollerskiis might be OK for training as long as wheels are
not too fast (inline wheels almost always are).

Having fenders is very important - your nice ski boots will turn
very dirty once you hit the wet road, and, believe me, you will.

Forget about using concrete surface - your poles will not "bite",
choose grainy asphalt instead.

You don't stop reliably on rollerskis - not abrupt, anyway.
Rollerski is go anywhere tool as long as you now where the
hell you are going. Choose downhills with safe roll-outs
before you get confident.

And last, but not the least - to get the feel, try rollerblades
with poles first, but don't stop there - it is not the same!