As a lefty who didn't get my first pair until my 40's, they aren't necessary but boy do they make cutting on a line WAY easier. Crazy differences in difficulty level for a clean cut.
It depends, most scissors now are practically ambidextrous. Some though, have really angled interiors of the handles that make them painful to use for an extended duration.
Using normal, right-handed scissors with the right hand works noticeably better. Cleaner cuts, and you can tell the handle is meant to be held with the right hand. I've used cheap/dull scissors that wouldn't even work with the left hand. Oh man, let me tell you about scissors...
Funny you mention cheap scissors because I've always thought that expensive scissors were more of an issue because they tend to be super specialised and as a result super handed
Every time I use right handed scissors I have Soo many issues, the paper usually folds or rips instead of giving me a clean cut, unless I used a certain part of the scissors to cut and no more. To the point that although it was uncomfortable, I used my right hand to cut things with scissors.
When I got older I bout myself a dedicated set of left handed scissors.. fucking amazing, I can make clean cuts with my dominant hand utilising the entire length of the scissors, and it works every time.
And those scissors are now the sharpest scissors in the house because I'm the only one who uses them, the other pairs of right handed scissors in the house are blunt af and barely cut even when I use my right hand.