All the previous posts have touched on the solution, and they're all correct.
It's important to analyze each component of your issue. With not a lot of dives under your belt, you'll have a lot of people telling you the "standard" way to proceed. And I'm here to say that you should feel free to deviate as soon as you're certified (which you are, so go ahead!). PADI is very rigid, but they have their reasons. But there's no point in a standard length hose if it doesn't fit the bill.
So, to your comment:
A reg pulling off to one side, or "wanting to come out" is
usually a function of hose length or rigidity. Look at my picture in my profile. That was a rental rig from a vacation dive with a hose that was too long and had a stiff outer wrap. Terrible!
You've had the suggestions: Miflex is softer and will curl a little better, and length is a whole subject in itself. Let's set Miflex aside for a moment (though I dive with my primary on Miflex) and look at length. There is one ideal length for your primary based upon which port you route from (and is your regulator mounted "up" or "down"?). That length will be perfect with your head in the midline, but will also allow you reasonable head motion to either side. A Miflex hose of that exact length will give you a little more flexibility. The problem with Miflex is that occasionally it has a mind of its own with regard to how it lays in the water (probably due to its braided covering), and it may be frustrating if it wants to curl differently. That's tough to accept if you've just spent $35 on a Miflex hose.
But then with length, a new complication arises. The issue of "streamlining" and minimizing drag is complicated by your hoses. The longer your hose, the easier it will be to move your head from side to side. However, the longer your hose, the more it might stick out to the side, and drag in current or when you swim. You've heard the next suggestion in this regard: adding a 70-degree connector to your second stage. That's what I do, but it comes at the price of people telling me that I have yet another "failure point" in my system. But it allows me to position the hose so it approaches the reg slightly from
below, so when I turn my head, there's no pulling on the hose at all.
To be honest, though, you'll probably get more criticism than you're prepared to answer at this stage of your career, if you start lengthening your hose and adding an angled connector.
The last piece was addressed first: your mouthpiece. All this talk of the Seacure neglected your comment about possibly needing a smaller mouthpiece. The Seacure is big. I might suggest a mouthpiece with the silicone pads on it, as it is easy to clench and is smooth on the outside, while not going so far into your mouth. That's this one:
Scuba Diving Black Silicone Octopus Snorkel Mouthpiece Color Tab Regulator Tie | eBay for the cheap version, and this one for the expensive Atomic Aquatics version:
Atomic Aquatics Regulator Dual-silicone Comfort-fit Mouthpiece - Pink
Another possiblity is the Comfo-bite. Some folks swear by them, but they're too short for me. It's worth $10 to try.
Aqua Lung.. Comfo-bite Silicone Regulator Mouthpiece 127826 with reviews at scuba.com Get some zip ties from the hardware store and just try different ones until you're happy. You have a great second stage in the G260, and the weight outside the water and size under the water are less important than its great performance. Don't let someone talk you out of it just because they think it's "heavy."
In summary, I'd plan on spending $50 trying two or three different hoses (or PM me - I'll mail you a selection of tested used hoses for cheap from my shop repair regs until you've got your length down). Also plan on $20 for a variety of mouthpieces until you're happy. Only then would I consider Miflex and long hoses with connectors. By then you'll have your preferences down, and will be ready to meet the criticism from someone who does it differently. The ideal hose length will change as your diving style evolves.
After 25 years, I dive a 5' hose clipped to my BC, that comes from below onto a 70-degree connector to my second stage. This way, I can hand off my primary to my buddy or another diver and let them have as much or as little separation from me as is appropriate, and the swivel allows them any position they want (facing me or parallel). Then, I breathe off my octopus, which is as good as my primary, and is on a very short hose (shorter than would be comfortable in some cases). They can grab my octo if they want, and that will put us in standard PADI hugging position. But I'd only do that with a regular dive buddy, because I know my buddy is not likely to panic, while he/she's only 1 foot away.
Have fun experimenting. Accept that it could cost you a few $$ (PM me if money is tight, or even if not). Then believe that what works for you is "right" no matter what someone else might say, until you change your mind again for good reason. I wish that you could just "buy a set of gear" and have it work, but as you've discovered, it's a very personal thing.