Not to butter you up or anything,
Now I want waffles.

Are potion/poison weights modified from vanilla?
Yes. Current design is that all potions and poisons weigh 0.3, which matches OOO's weight for pre-made potions. I may return to the vanilla 0.5, as there are good arguments against letting the player carry too many potions, and obviously they're pretty big in Tamriel (water aids digestion!); on the other hand, all magic (potions included) is a bit weaker now so it might not be a problem. I'd argue that between the weight of the bottle, the fact that poisons might be produced as paste (less liquid weight and volume), and the good ol' KISS principle, there's no reason to have two different weights.
This is one of the places where I want to create consistency between pre-made and player-made potions, which unfortunately makes it difficult to let potion weight be user-configurable or I'd just do that. I can safely set player-made potions to any arbitrary weight with a script, and I can tell poisons from potions; but I have no reliable way of telling the difference between a generic pre-made potion which
should be adjusted, and a special one which
shouldn't. Should some mod introduce, say, a Potion of Dark Matter which weighs 50 for some meaningful reason, I don't want to break it.
As far as bound items go, are they still duration based?
Yes, but they're much less expensive. Because they can't be enchanted, I felt bound items needed to be much more attractive. The durations are longer and most of the spells are still cheaper and available at lower masteries.
If you have at least 25 Heavy Armor skill, even one piece of bound armor is a better deal for your magicka than Resist Normal Weapons (which is replacing Shield as the low-level survival effect). Of course, you can use both effects at once for even more protection. The Shield effect is
much more expensive because it stacks additively with armor and has no weakness to silver/daedric.
Bound weapons have been a lot harder to put a value on. They need to be good enough that you might use them instead of a long-duration fire spell (which has the advantage of not needing to stand next to the enemy expending fatigue), but not so good that you just ignore all weapon loot until you pick up a minor artifact. Frankly a big part of the problem here is the ridiculous damage scaling, which MOBS smooths out but does nothing to fix, and OOO actually seems to make a bit worse. Far smaller differences could still be significant enough to warrant upgrades. But that's a different project and for now I've got to work with what's generally used... so, this looks like a job for playtesting!
Are more spells going to be added (like push/pull, poisons, short range teleport, etc etc) and if not, will it play nice with the likes of LAME and SM as in using spells added by these, but overwriting settings based on load order?
No scripted effects will be added by Ars, but it should be fully compatible with other mods which add them. (Balance is another question, but that's left up to the user.) Permanent summoned items would fall under this category.
Note that SM does some scripted settings changes which won't be overridden by load order, but can be disabled in its configuration. Then again, only thing I remember specifically is magicka regeneration, which I may not directly address in Ars because nGCD does a much more thorough job. Maybe I'll put out a stand-alone, more lightweight version of that... call it Pool-Independent Magicka Potentiation (PIMP).
Regarding your Crazy Idea: when I make it back around to updating Progress, you might see something you like among the optional modules.