If you are not creating a new item on Board 2 with the Connect Boards Column (for example, through an automation recipe like “when X happens, create item in Board 2 and connect it to Y item in Board 1”), it won’t affect the number of items you can have on a board at all.
The linked item limits are about how many items you can connect into one board or one Connect Boards Column or cell - not about how many items you can have on a board that is connected to another board.