There’s implications of Legion using other tech improvements as well in game. Rex has a faded Legion Bull on his side implying that prior to his ownership by the King he was used by the Legion. That would require an advanced understanding of tech in order to maintain him with the assumption he was eventually traded to one of the caravans that pass through Arizona for supplies once he was too run down to continue as a dog of war.
That's likely a reference to Van Buren again. Denver, aka Dog City, is completely overrun with feral and wild dogs, altho there is also more advanced cyber-dogs and even prototype robot dogs as well. Actually, I think one of the endings clearly states that Rex served as a police dog in Denver before the war, and we know Legion gets some of it's best dogs from there(in Van Buren, one of the few encounters with The Legion would be in Denver). It's less accurate to say that Legion has a special division of Cyber-Dogs or use them in battle, and moreso that they simply found him and he was kept as a curiosity, maybe a personal pet of Ceasar. If you bring Rex to Anthony, he flat out says he was lost in a battle of Denver, so I guess he traveled all the way from there to Freeside somehow.
I personally don’t consider much of what base New Vegas says of the Legion as canon. It’s so watered down and nonsensical to the direct statements that Caesar makes in his spiel. It makes more sense that there would be a conceited effort to have members of the Frumentari or another segment of the Legion to have an understanding of the tech in order to utilize it to further their own goals. Caesar notes this with his statement that his Legion is the hypothesis, the NCR and the Old World their antithesis, and when the two clash his Legion will achieve a synthesis. New Vegas states this but fails to express it in the story. Instead Caesar spergs about random things supports the cannibals, etc, etc.
The Frumentarii do their best to blend in with whatever civilization or tribe they're infiltrating, that of course means learning about their customs and technology they use, but it's clear that Ceasar is banning use of technology, science and medicine for his own soldiers so that they don't end up depending on it. Ceasar isn't Ted Kaczynski, he has his own Auto-Doc and even a high-tech power fist, it's clear he understands technology and has people that also do. It's just that outside of his own needs, he makes sure it's used as little as possible, and tries to keep it away from his men so they don't grow weak by abusing it. Remember, Legion teaches it's people Roman mythology and Ceasar tells his men that he is the Son of Mars, this means that keeping his society low-tech is not just practical when most of them are easily fooled uneducated tribals but also has a secondary goal: making sure nobody knows that he's making this up as he goes along. Most people serving him are ignorant tribals that don't know better, the lore states that anyone actually educated in their lands, like Followers, get killed on the spot. Last thing Ceasar needs is some of his soldiers finding a history book or a working holotape and finding out about the real Roman empire. The only technology Ceasar would be entertaining using is whatever is immediately needed by him and his army right now, so his Auto-Doc to keep himself alive and weaponry for his soldiers, like the artillery gun or energy weapons from the Van Graff deal. Everything else is forbidden unless Ceasar makes an exception for it, makes sense to me. As for the cannibals(White Glove Society) it's clear he only needs them so that they help him take over the city and weaken it before he arrives with an army there. He also recruits Omerats to stage a massacre on The Strip and plant explosives all around The Strip, the plan is to terrorize Vegas while his army is busy taking The Dam, by the time his soldiers arrive in Freeside there should be much less opposition. He plans to integrate Omertas and White Gloves into his society just like has has with 76 former tribes, ie buck breaks them and crucifies anyone who offers any resistance, then takes the women and enslaves them. He and House are the only ones with any long term plan, Yes Man literally just goes along with what you do because he has no choice and NCR is only there for the resources and land, it's actually a good bit of writing. And yes, Ceasar is a hypocritical prick that isn't nearly as smart as he thinks he is and often times contradicts himself, that's his character. Only his ignorant men think of him as some sort of second coming of Mars here to help them reclaim The Wasteland, because he indoctrinated them, everybody else sees him as a petty tyrant.
The outlawing of modern medicine I took to be keeping the literal tribals who were years removed from it away from highly addictive drugs that would compromise your fighting force. Once the battles over and the Legion can settle those types of laws would likely be laxed to focus on the recreational instead. The game never mentions it but I can’t imagine injecting yourself with a stimpak 4 times in a row can be healthy.
This is the setting that has very powerful healing tribal herbs and remedies, like Healing Powders or Hydra. It is perfectly understandable that Ceasar would simply not need to depend on stimpacks of the old world anymore, which is actually really smart. Those will run out eventually, and even tho you can make more, you still need the know-how and the tech to make them, which his army lacks. All you need to make powders are the right ingredients, on the other hand, which are plentiful. They also weight less, which is important for an army that is on the constant move and usually has to live off the land. NCR, on the other hand, needs to depend on constant supply runs and has complicated logistics, something that is a massive issue at the time of the game and is easily exploitable. Only Rangers can live off the land in a similar manner, and they're few in numbers compared to the mundane troops. Ceasar is making sure that almost every single man is on par with The Rangers, and without the need for non-renewable resources or high-tech weapons. This strategy would have worked too, Legion only lost the first battle because Hanlon laid a trap for them. They took over The Dam, and would have held it too if they didn't pursue the escaping troops.
Anyways, I doubt Ceasar would allow recreational drugs in his society, they do nothing but poison it. Recreational herbs maybe, but only because it's too much of a pain in the ass to fully enforce, much like prohibition in the 20s. I could see Ceasar eventually introducing some minor tech like stimpacks in his Pax Romana, but that would be long after he conquers, or otherwise integrates, all of post-war America that he is realistically able to hold, and even then he will probably be dead by the time this would be introduced. But now we're going into even deeper "what ifs" on how would Legion controlled territory look like 20-30-50 years or more after their victory in Mojave. For all we know, victory or not, Legion will still collapse almost immediately after his death and it's a moot discussion.
