Experience definitely goes to the Slayer and while I couldn't argue a skill debate to save my life, Wolf isn't a slouch. If I could, I'd argue he could keep up if not surpass the Slayer. At least with a sword.
The match description seems to indicate that they start rather close, I'd say within that 'tens of meters' mark. Considering range, if the Doomguy uses his Railgun for a major wincon the match won't be counted as it is faster than Speed Equalised Sekiro (Same with the Haste Ball). As previously stated though, he is much more likely to close the distance.
Despite his time period, Wolf has experience against opponents with firearms. Namely the Snake Eyes, Interior Ministry Red-Guards, and the Glock-Saint. While their weapons aren't as advanced he should be able to identify the Slayers weapons as he pulls them out instead of when they fire, giving him a chance to dodge instead of just blocking.
(While he is described as Shura here and doesn't fight the latter two, the profiles seem to composite Endgame Wolf anyway so, eh.)
Good Dodging and Deflecting combined with the Loaded Umbrella which Wolf can pull out in an instant should be able to withstand the Ballistic side of the Slayers Arsenal, at least until he closes the distance. Said Umbrella shield can defend from all angles while he pushes forward and the Mist Raven Feather can be used to teleport closer upon being hit by an attack. That being said, any Plasma Weaponry debatably just melts through his gear.
Sekiro has his own, albeit limited, arsenal of ranged options through his Shuriken and Dragon Flash. Though he's more likely to simply use them as harassing tools to get close.
While Melee combat is most definitely where the Slayer is physically strongest, Wolf's combat style is pretty much all about keeping his target on the defensive waiting for the one slip-up that will grant him the win through one or two Deathblows. That being said, Pressure Points are probably going to be a bit difficult considering the Praetor Armour's fully enclosed setup. Unlike the Armoured Knight, however, he has the advantage of having the Mortal Blade here which theoretically should be able to cut through.
If the Slayer has the higher AP, then Wolf isn't unaccustomed to going against foes who take a chunk more to kill. He has the Healing Gourd and Pellets to keep him running which will make killing him difficult even if he doesn't have access to his revives. But I would like to know the Lifting Strength value for certain. As if the Slayer does have an advantage it will make CQC much more dangerous.
Despite Sekiro being a Shinobi, the open field doesn't lend itself to Stealth, Slayer has Enhanced Senses and VEGA to spot Wolf if he tries. Though I'm not entirely sure how much help the AI provides this version of Doomguy.
