Is it okay to have a 2d magnetic chess set next to your score sheet? And as you play, you move along with the pieces. I like looking at a 2d board better because it's smaller and I'm used to playing on my computer. I look at the 2d board and then play on the 3d board. After I've made my move on the 3d board. THEN I move the pieces on the 2d board. Is there a rule against playing like this in tournament?
I'm pretty sure the rules of most serious tournaments prohibit the use of a second board for any reason, but I'm not sure if there are special provisions for people with disabilities and disadvantages.
As a player, I would be quite apprehensive towards playing someone who is using a second board, simply because it means I have to keep an eye out to ensure he is not cheating. I would certainly have a word with the arbiter if that situation were to occur.
I am assuming you're talking USCF rules. Using a 2nd board is against USCF rules.
In fact, during one of the world championships, one of the players used the overheard board being displayed to the audience and eliciting a complaint by the other side. FIDE rules are not exactly like USCF rules, by the way.
I think that in most chess tournaments with classical time controls, having a 2D chess board next to you while playing is not allowed. That being said, I would recommend against this sort of practice all together. I can understand your reasoning and the possible motivation to have a 2D chess board. Yet, dealing with the 3D chess pieces is part of competitive chess. The earlier you get used to this, the better you will cope in your future games over the board.
I think that in a FIDE tournament you would fall foul of article 11.3a
During play the players are forbidden to use any notes, sources of information or advice, or analyse any game on another chessboard.
While demonstration boards are allowed in the playing area the problem here is that you have control of the pieces. The fact that you claim you are only moving the pieces on the 2d board after the moves on the main board and then only to match the main board is irrelevant.
The implication of allowing you to even have this board next to you is that an arbiter would have to stand over you full time to ensure you don't start analyzing. In other words, "No way!"