Usually I start with the side reins there but not shortened. As I start adjusting them over a period of days, I unclip them, shorten them, and doing up the outside first, I then clip up the inside, prepared to send the horsse immediately forward, on the longe.
Some riders change their horse, they change their saddle, they change their teacher; they never change themselves.
I introduce side reins as a part of the total process of learning to give to pressure. Before the horse ever has any reins on, they learn to give to pressure from ground work, first with a rope halter, then with a bit. I usually ground drive in a rope halter and later a bit BEFORE introducing side reins, then I will use side reins, fairly loose at first and gradually shorten them. Never had any issues using this method
I like the idea of Vienna Reins also. I definately dont use side reins of any kind until the horse has learned to give to pressure in the mouth first. Long Lining can be a great option for this. I have long lined all of my young horses to teach them to yield to pressure in the mouth.
So much depends on the horse. I introduce the idea of giving to pressure right away with a young horse, using a halter. Stand tied, back up, circle in both directions, etc. I will also stand on one side or the other, reach up, and press down on the poll with a moderate but not increasing amount of pressure. The moment the horse lowers its head, I give. Lather, rinse, repeat about 100 times, and in different locations. Stand to one side and bring the head around without twisting the neck, so there is proper bend in the neck. Move the hind quarters over. Do it all later in a bit. Like others, I long line, you can do a lot this way. It has never been an issue, not really.