Okay let me help out first, tension and brakes are two totally different animals. Tension is a constant force, all that means no matter what that spool is doing, stopped, spinning, the tension force does not change. Brakes are a reactive force, that kick in after the cast and are dynamic. The amount of force they put on the spool varies from the amount of brakes you have on, to the speed of the reel.
Before I go any further let me clarify, brakes are not a bad thing, and I don't care if you use them.
Being that brakes affect the results of the input from your cast/swing, they can be really good at hiding any flaws in your swing, or casting mechanics that create a backlash in the first part of your cast. Spinning rods are very forgiving, it's not just the reel that you are going to have to learn how to use. You are going to have to learn the impact of not knowing how to swing a rod efficiently.
The whole reason I say not to learn with brakes and on tension, is because it is going to show you and teach you a lot more about the cause and effect of a good cast or bad one. It is going to make you start off with smooth gentle sidearm cast that won't go far, but you are going to learn way more about yourself doing it this way then by jacking up the brakes and the tension so you can cast overhand.
You can learn how ever you want, for me I like to start off with all new things making sure I use the best techniques I can. This makes the first few cast more difficult, but it also in my option is going to force you to slow down and learn far more then just setting the tension and brakes so that you can go fishing with it.
To me buying your first baitcaster and thinking you should be able to cast with it right away is just not the way you learn. That is the way you get to use the reel, and casting.
I think a lot of people are stuck on the reel aspect too, if you can't use a rod, it is only going to make using a bait caster that much harder.
When I am fishing, and looking for long casts, I drop the brakes, and as much tension as I can. My casting style is smooth, and graceful, I don't whip with all my might to over power my tackle and waste energy. In my experiences the more brakes you use the the less thumb you need, but even a high tension with no brakes still needs a thumb.
It is not two equal forces, and lowering one and raising the other might net you the same results, but brakes whole purpose is to decrease the energy that you put into the spool the more energy the harder they work. Sounds to me like you can correct this problem for the most part with the rod and a smooth cast and for the most part be a much more efficient fisherman by not using brakes at all. Allowing you to fish longer with less fatigue.
I do know the lighter the spool is, the less resistance to spinning it has and less force it takes to start moving it. I also know that overruns are a simple case of the spool having more energy and motion then the line or the lure. Given that I would say focusing on learning good mechanics from the start is a much better option then the instant gratification you might get from brakes.
Again this was about learning to cast, and not about how to get the most from your reel.
For me I can cast any reel with no brakes, I don't need to turn them on in order to cast far, or be productive. I also find that even when I take a little tension off with brakes on, I can not cast as far as when I have the brakes off. I have to use more effort in my cast with brakes to hit the target even with less constant spool tension.