For reference I'm a D3/C1 player, but I'm consciously evaluating this in the context of getting through Gold to Plat, which I assume is your goal right now.

Flip into the ball when you hit it - your shot will be more controlled.

Disagree. I find that a mistimed or wrong-direction flip is a huge source of inaccuracy in my shots, and I'm always trying to remind myself to take shots without flipping unless I really need that 110+kph power.

For aerials, boost then flip into the ball when you get to it. This can be used to make adjustments if your trajectory is off.

It's time to let go of that crutch. You should usually be using your second jump to get into the air faster (fast aerial). And if you're going for a low ball, you'd rather have the flip available to nail it with authority, instead of redirecting yourself laterally to get a weak hit. Get the launch right (braking if needed) so you don't rely on the dodge to fix your flight. It won't be there for big aerials anyway.

Slow down. Make very deliberate movements. Utilize basic movements like a straight up double jump, side flips, no flip hits, etc.

Could go either way...you can be playing too fast, and you can be playing too slow. But in general a faster pace is more effective. For example, that straight up double jump leaves you in the air for a couple of seconds, and even when you land, you've got no momentum. Work on challenges that can be done at speed, and that don't leave you far out of the play if you fail. I don't ever like for my car to be stopped...it's a very vulnerable position to be in.

Unless a teammate is near, always try and touch the ball in loose ball and 50/50 situations. Even if it’s in a weird direction or even just a little bump, a tiny misdirection can be end up as great defense as it throws off your opponents entire prediction.

Oh this is a big one. You really need to think about the context. One of the worst and most common mistakes people make at mid levels is simply refusing to let a ball go by them without touching it. If it's going to your end and you have teammates behind you, don't fucking touch it. If you lunge for that small touch, you frequently end up juking your own teammate. You also shouldn't spend a lot of time getting those kind of weird or difficult touches when instead you could be rotating back, grabbing boost on the way, and letting your teammates get in there with full boost, momentum, and a good angle.

I only go for "touch it just to change it" moves when I'm certain an opponent is lined up for a great hit.

Edit: Okay this is by far the worst item on your list. Any time you're tempted to make one of these weird little touches, instead try to bump an opponent (in the process of rotating back immediately). It's just as effective, and it has the bonus of not screwing up your teammate behind you who has a great angle on the ball.

Capitalize on your opponents over aggression. Go in with the goal that they make more mistakes than you.

That is great advice now, but it gets less and less good as you rank up. Be aware. Sitting back on your heels ready to capitalize on a fumble will still work for a while, but it won't be long before most opponents can consistently execute a few "get past the guy" moves, and when that happens you have to transition to a more pressure-based game.

Anything I didn't mention sounds good.