As i don't usually watch gymnastics and now watched some i was wondering:
1) is the scoring system similar with figure skating?
2) are the gymnasts (girls) a bit bigger and more muscular than the figure skaters or is it just a illusion cause there're outfits are so overly

tight.... why on earth is this.....?!
3) are there (or has there been) elite skaters that used to be primarily in gymnastics and same question in opposite.
1. A bit similar. A score is based on the combination of the difficulty (D-score) and execution (E-score) of a routine, much like a technical and component score in FS. Each jump, leap, tumble, and spin is given a difficulty level (A=0.1, B=0.2, etc.). Each routine has a required number of elements, much like the SP and FP and you are not allowed to repeat an element if you miss it like in FS. Everyone starts at a 10 for an E-score and are then deducted from that, not added.
99% of the time, a routine is planned in advance and the judges know what you plan to execute beforehand, although you don't get deducted if you change things around as long as it fits the requirements. Choreography and interpretation are factored into the execution score for the floor exercise. One thing that is not factored in the score is the costume/uniform (which is always a leotard).
2. Gymnasts are in general, much, much smaller than figure skaters (4'11"-5'02"). Lipnitskaia would be on the verge of being tall for a gymnast. McKayla Maroney and Kyla Ross at 5'4" are considered very tall while Sandra Izbasa at 5'6" is a giant (tallest gymnast to win an Olympic gold medal, and she did it twice at different Olympics!). You really don't see female gymnasts taller than that due to the biomechanical demands of gymnastics that doesn't allow routines for tall people to be feasible.
Gymnasts are much more muscular than figure skaters, though. Look at Shawn Johnson: she was barely 4'8" when she won gold in Beijing, but she is jacked. An article perfectly describes why gymnasts are bulkier than the leaner figure skaters:
‘In gymnastics, shorter, muscular gymnasts tend to be better at flipping; thinner gymnasts twist more easily. Each selects her skills accordingly. The same physics applies in skating, except that there are no flips on the ice (unless you’re Surya Bonaly). Every skater has to twist. This means everyone has to be thin, which means every top-flight figure skater has a similarly lean figure.’
As for why they're leotards are so tight... I have no answer. You haven't seen tight though until you've seen Catalina Ponor in her leotards. They be riding up in the back AND the front.
