First, a disclaimer- there's a lot of material relevant to the Mandalorian Wars I haven't read. So if any of the below is contradicted by a canon source, please feel free to correct me.
That said, given what I know of the Mandalorian Wars, Revan doesn't actually need to be a peerless tactician- she has underlings for that. The Republic had an enormous advantage in size and industry over the Mandalorians, and in all honesty, I think that as long as Revan had a solid grasp of Strategy and a good understanding of Logistics, the outcome of the Mandalorian Wars was pretty much inevitable. In a lot of ways it's actually pretty easy to draw parallels to the American Civil War- The Confederacy won a number of battles at the beginning by virtue of having better generals then the Union, but the Union was always going to hopelessly outclass them in terms of Industry and Logistics. Similarly, while the Mandalorians started the War with superior troops and officers and won a number of victories, the Republic was always just that much bigger then them. All it needed to win was for the Military Command to properly understand those advantages, to turn it's massive industrial might towards warmaking, and apply it accordingly.
Which isn't to say that the Republic couldn't have lost the war, but I think that'd have more to do with a political failure then the Mandalorians conquering everything. The Republic has a lot of space to trade for time at the end of the day.
Now, this isn't to say that Revan is a terrible general. She was probably a good tactician who could and did manage fleet engagements and ground battles. It's just that the real skills she needs to win the war for the Republic have more to do with managing the logistics of a massive war machine, building a decent officer corps, understanding the strategic necessities of the campaign, maneuvering through the various bureaucracies of the Republic to get them to give her what she wanted, and the charisma to get everyone to give her all that power in the first place. Tactics is kind of secondary to all of that.
Basically, Revan's role in the Mandalorian Wars was probably more Eisenhower then Patton. While she certainly ended up in tactical command and lead from the front on numerous occasions because this is Star Wars and she's a Jedi, that probably wasn't the most important thing she was doing, really. Or at least it shouldn't be, not with a war on this scale. So I honestly wouldn't be surprised if Thrawn could beat her in a fleet engagement where they both have comparable forces. Thrawn's ability to understand his enemies and their blind spots is practically witchcraft, and there was probably a fair amount written about Revan's command style. If he knows who she is, and has access to some or all of that, I'd give him good odds in fighting her. It's his thing.
It's just that they aren't going to be fighting in a giant featureless box with equal forces. Revan's charismatic, the Empire is corrupt and evil to an almost absurd degree, and Revan is already convincing large numbers of Imperials to defect. If Revan ever learns of the Noghri, it's perfectly possible that Thrawn will die the exact same way he did in his trilogy.
Also, she has one of the better practitioners of Battle Meditation working for her. That counts for a lot.
