i must admit i do wish that they had put vulcan ears on him when he was on the enterprise B. Even if they had not mentioned his name it would have been cool, as we could guess he was the same character.
That might have been neat, yes, but Voyager hadn't even started yet when Generations came out, so there wasn't anything to reference yet.
In the Voyager episode "Flashback" his Ent-B appearence is retconned. It was indeed Tuvok onboard the Excelsior, they even make his ears pointy. In that episode he states clearly to Janeway that he left starfleet after this as he couldnt fathom the actions of Captain Sulu and some other crewmen, he hadnt learnt how to intergrate into a mainkly human crew yet which was something he struggled with still in the late 24th Century. He could very well of been a 31 member, the writers have indicated they intended one of the Voyager crew to be a 31 member but we never saw it on screen. It has however, been included in other books and added to soft canon
If you want my personal opinion, I think it was Paris who was the 31 Agent on board. No matter how much influence Janeway thinks she had, there is no way she could of successfully freed a traitor from an Earth Penal Colony just so he could pilot the ship through the badlands. Paris' Father is a Starfleet Admiral so Paris would of been usful for 31 if they needed information. Paris was the one who got kicked out of the Marqui for getting caught by Starfleet Security and giving them information... how could you not assume that was his mission all along?
All in all, I dont think Tuvok is an Agent... it wouldnt be Logical for him to do so
People always want to involve Section 31 in everything. If you look at your RP communities, they're literally crawling with active Section 31 operatives, former Section 31 operatives, and characters sworn to its destruction. It cheapens Section 31. Turns it into a joke. It was interesting when it was new. This covert organization that interrogated and then tried to recruit Bashir (which would've been a good way to keep their existence secret) that is as old as the Federation itself. There's been speculation that Section 31 was behind the Ba'ku debacle, what with the holoship, the secrecy, relying entirely on outsiders for their military needs (where was Daugherty's ship?). I liked that. I could see how that could be true, but there was no proof.
Then it turns out Archer finds out about it before the Federation even exists, that one of his officers worked for it, and (according to the ENT novels) one of his officers would fake his death to join them. It gets exceedingly hard to believe Section 31 is competent enough to keep its existence a secret for one year, let alone two hundred.
And if nothing else, Section 31 has human origins. Although (fortunately) we've not seen that many of their operatives, the ones we have seen were all human, even in the twenty-fourth century. I doubt non-humans are very well represented within their group. In part as many Federation worlds have their own, clandestine or otherwise, intelligence agencies. Vulcan has V'Shar. The Andorians (according to soft canon) have Am Tal.
While I think Tuvok probably would elect to work with Section 31 when presented with stakes high enough - he is Vulcan afterall - I would still avoid linking them for no good reason. A connection to Section 31 at this point is not an automated improvement to the character or to the origanization, from a story telling perspective.
Trek is full of actors who have played multiple characters over the course of its history, and not always the same character. Sometimes it's a case of Hey, It's That Guy!, and sometimes the prosthetetics are so heavy that the actor is virtually unrecognizable (unless you are familiar with the voice). So to say that Tuvok was a Section 31 agent based on the actor's many appearances as a character *other* than the one he's famous for is, in my honest opinion, pretty thin...